GF Texas Sheet Cake with Fudgy Chocolate Frosting

GF Texas sheet cake is a thin, tender chocolate cake baked in a large pan and covered with warm, pourable chocolate frosting. This gluten-free version uses a measured all-purpose gluten-free flour blend and a buttermilk-based batter for a soft crumb, while toasted pecans add the classic optional crunch.

Ingredients

2 cups (280 g) all-purpose gluten-free flour blend with xanthan gum
2 cups (400 g) granulated sugar
1 teaspoon baking soda
½ teaspoon fine salt
1 cup (226 g) unsalted butter, cut into pieces
⅓ cup (28 g) unsweetened cocoa powder
1 cup (240 ml) water
2 large eggs (about 100 g without shells), at room temperature
½ cup (120 ml) buttermilk, at room temperature
1 teaspoon vanilla extract
For the frosting: ½ cup (113 g) unsalted butter, cut into pieces
¼ cup (21 g) unsweetened cocoa powder
6 tablespoons (90 ml) milk
3 cups (360 g) powdered sugar, sifted if lumpy
1 teaspoon vanilla extract
½ cup (55 g) chopped pecans, optional

Instructions

Set a rack in the middle of the oven and heat it to 350°F (175°C). Grease a 13-by-18-inch rimmed half-sheet pan, then line the bottom with parchment if you want easier serving. Check that the flour blend is labeled gluten-free, especially if baking for someone who must avoid gluten.
In a large bowl, whisk together the gluten-free flour, sugar, baking soda, and salt. In a medium saucepan, combine the butter, cocoa, and water. Warm over medium heat, stirring, until the butter melts and the mixture just reaches a gentle boil; take it off the heat promptly rather than reducing it.
Pour the hot cocoa mixture over the dry ingredients and whisk until smooth. In a separate bowl, whisk the eggs, buttermilk, and vanilla together. When the chocolate batter is warm rather than steaming hot, whisk in the egg mixture until fully incorporated. The batter will be fairly thin.
Pour the batter into the prepared pan and spread it evenly into the corners. Bake for 18–22 minutes, until the surface springs back lightly when touched and a toothpick in the center comes out with a few moist crumbs but no wet batter. Avoid waiting for the cake to become dry. Set the pan on a cooling rack while you make the frosting; it should still be warm when the frosting goes on.
For the frosting, combine the butter, cocoa, and milk in a saucepan. Heat over medium-low, stirring, until the butter melts and the mixture is smooth; do not let it boil hard. Remove from the heat and whisk in the powdered sugar in a few additions, followed by the vanilla. Stir until glossy and pourable. If it seems too thick to spread, whisk in milk 1 teaspoon (5 ml) at a time.
Pour the frosting over the warm cake and spread it gently to the edges. Sprinkle with pecans, if using. Let the cake stand for about 35 minutes, or until the frosting is set enough to slice. Cut into 20 squares and serve.

Tips

Use a gluten-free flour blend designed for baking and containing xanthan gum. If yours does not contain it, add ½ teaspoon xanthan gum to the dry ingredients. Blends vary in absorption, so weigh the flour when possible and avoid adding extra flour just because the batter looks loose.
Bring the eggs and buttermilk to room temperature so they blend evenly into the warm chocolate mixture. If the cocoa mixture is very hot, let it cool briefly before adding the eggs to avoid scrambling them.
Spread the frosting while the cake is warm: it will flow across the surface and set into a thin, fudgy layer. If the cake has cooled completely, the frosting will still work, but may be harder to spread evenly.
For a nut-free cake, simply leave out the pecans. For reliable gluten-free serving, use clean bowls and utensils and check that all packaged ingredients are labeled gluten-free; avoid cross-contact with flour or crumbs.

Serving Suggestions

Serve the squares at room temperature, when the cake is soft and the frosting has set. A small scoop of vanilla ice cream or a spoonful of lightly sweetened whipped cream pairs well with the cocoa-rich topping. For a less sweet plate, add fresh strawberries or raspberries. The cake is rich, so modest squares are usually enough for a dessert spread.

Variations

For a deeper chocolate flavor, use Dutch-process cocoa only if your baking soda and flour blend are compatible; natural unsweetened cocoa is the dependable choice for this recipe’s leavening. Stir ½ cup (85 g) mini chocolate chips into the batter for extra pockets of chocolate, though the cake will be sweeter. You can also replace the pecans with ½ cup (55 g) chopped walnuts, or omit the nuts altogether.

If you do not have buttermilk, stir 1½ teaspoons lemon juice or white vinegar into ½ cup (120 ml) milk and leave it for 5 minutes before using. This quick substitute adds acidity and behaves similarly in the batter, though real buttermilk gives a slightly tangier flavor. Do not use a one-to-one swap with coconut flour or almond flour; they absorb liquid differently and will not produce the same cake.

Storage and Reheating

Because this cake contains eggs and dairy, refrigerate leftovers within 2 hours of baking or serving. Cover the pan or transfer slices to an airtight container; they keep for 3–4 days in the refrigerator. The frosting firms when cold, so let slices sit at room temperature for 20–30 minutes before serving, or warm an individual piece in the microwave for about 8–12 seconds. Avoid heating until hot, which can dry the cake and melt the frosting unevenly.

For longer storage, freeze individual unfrosted or frosted slices in a single layer until firm, then wrap well and place in a freezer-safe container for up to 2 months for best quality. Thaw overnight in the refrigerator or for about an hour at room temperature. If reheating leftovers, USDA guidance is to heat them to 165°F (74°C); for cake, a brief microwave warming is generally intended only to soften a serving, not to hold it hot.

Frequently Asked Questions

Is this Texas sheet cake completely gluten-free?
It can be, provided the flour blend and every packaged ingredient are labeled gluten-free and you prevent cross-contact from shared utensils, pans, or countertops. Check labels on cocoa, powdered sugar, and any add-ins when cooking for someone with celiac disease or a serious gluten sensitivity.

Can I bake it in a smaller pan?
A 13-by-18-inch rimmed sheet pan gives the traditional thin cake and the bake time listed. A 9-by-13-inch pan is smaller and deeper, so the cake will take longer to bake and may not have the same cake-to-frosting ratio. Do not fill a pan close to the rim; use a second pan for excess batter if needed, and check doneness in the center.

Why is my gluten-free cake dry or crumbly?
Too much flour, overbaking, or a blend that absorbs more liquid can cause dryness. Measure by weight when possible, start checking at 18 minutes, and take the cake out as soon as the center is set. Allow it to cool before cutting so the crumb can settle.

Can I make the cake ahead?
Yes. Bake and frost it the day before, let the frosting set, then cover and refrigerate. Bring it toward room temperature before serving for a softer crumb. You can also bake the cake ahead and frost it once warm on the day you plan to serve it.

Do I have to use pecans?
No. Pecans are a traditional-style topping but are optional. Leave them off for a smooth frosting, or use chopped walnuts if nuts are suitable for your guests. Keep the cake plain if you need to avoid all tree nuts.

Can I use a dairy-free substitute?
You can try a plant-based butter stick and unsweetened, unflavored plant milk in both cake and frosting, but results vary by product. Use a dairy-free buttermilk substitute made by adding lemon juice or vinegar to plant milk. The flavor and frosting texture may differ, and the cake will not be suitable for guests with soy or other ingredient allergies unless labels are checked.

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Safety notes: safe minimum internal temperatures from USDA FSIS; raw and undercooked fish guidance from the U.S. FDA. Food safety notes

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