Vanilla Birthday Cake

A low FODMAP vanilla birthday cake made with a gluten-free 1:1 flour blend, butter, eggs, and lactose-free milk, with vanilla buttercream and sprinkles.

Prep 30 min

Cook 30 min

Serves 12

Gluten-freeVegetarian

Ingredients

For the cake

• 2 1/2 cups (350g) gluten-free 1:1 flour blend, rice and starch based (avoid blends built on chickpea, lentil, or soy flour)
• 1 tsp xanthan gum (omit if your flour blend already lists xanthan or guar gum)
• 2 1/2 tsp gluten-free baking powder
• 1/2 tsp salt
• 3/4 cup (170g) unsalted butter, softened
• 1 3/4 cups (350g) granulated white sugar
• 4 large eggs, room temperature
• 1 tbsp vanilla extract
• 1 cup (240ml) lactose-free milk, room temperature
• 1/3 cup (about 60g) rainbow sprinkles, certified low-FODMAP or label-checked (no honey, high-fructose corn syrup, inulin, chicory root, sorbitol, mannitol, xylitol, maltitol, or isomalt)

For the vanilla buttercream

• 1 cup (226g) unsalted butter, softened
• 3 1/2 to 4 cups (420 to 480g) confectioners' (powdered) sugar
• 2 to 3 tbsp lactose-free milk
• 2 tsp vanilla extract
• Pinch of salt
• Extra sprinkles, for decorating (same label check)

Instructions

Prep the pans

1. Heat the oven to 350F (180C). Grease two 8-inch (20cm) round cake pans and line the bottoms with parchment.
2. In a medium bowl, whisk together the flour blend, xanthan gum (if using), baking powder, and salt. Set aside.

Make the batter

1. Beat the softened butter and granulated sugar with an electric mixer on medium-high for 3 to 4 minutes, until pale and fluffy.
2. Add the eggs one at a time, beating well after each, then mix in the vanilla.
3. With the mixer on low, add the dry ingredients in three additions, alternating with the lactose-free milk, starting and ending with the dry. Mix just until no streaks remain.
4. Fold in the sprinkles by hand with a spatula, working quickly so the colors do not bleed into the batter.

Bake and cool

1. Divide the batter evenly between the two pans and smooth the tops.
2. Bake for 25 to 30 minutes, until the tops spring back and a toothpick inserted in the center comes out with a few moist crumbs.
3. Cool in the pans for 10 minutes, then turn out onto a rack and cool completely before frosting.

Frost and assemble

1. Beat the softened butter for 2 minutes until smooth. Add the confectioners' sugar 1 cup at a time on low speed, then the vanilla and salt.
2. Add lactose-free milk 1 tablespoon at a time and beat on medium-high for 2 minutes, until light and spreadable.
3. Set one cooled layer on a plate, spread with buttercream, top with the second layer, then frost the top and sides. Finish with extra sprinkles.

Tips & Substitutions

• Check your flour blend for gums. Many GF 1:1 blends already contain xanthan or guar gum. If yours does, skip the added xanthan so the crumb does not turn gummy.
• Read the powdered sugar label. Confectioners' sugar is sucrose plus a little cornstarch, both low-FODMAP. Avoid specialty blends that add inulin or chicory root.
• Vet the sprinkles. Most sugar-based sprinkles are fine, but scan for honey, high-fructose corn syrup, inulin, or sugar alcohols like sorbitol and maltitol. A certified low-FODMAP brand takes the guesswork out.
• Bring dairy and eggs to room temperature. Cold butter and eggs will not cream properly, which gives you a dense cake and a broken buttercream.
• Turn it into a sheet cake. Pour the batter into a greased 9x13-inch (23x33cm) pan and bake for 30 to 35 minutes, then frost in the pan.
• Dairy-free version. Swap the butter for a plant-based block and use a low-FODMAP milk such as almond or macadamia. The texture is slightly softer but still holds a layer.

Why This Works

• A gluten-free blend removes wheat fructans. Wheat flour is the main FODMAP concern in cake. A rice-and-starch based GF blend keeps the structure without the fructan load.
• Xanthan gum is low-FODMAP. The recipe uses a small amount, and it replaces the elastic network that gluten normally provides.
• Lactose-free dairy. Butter is mostly fat with very little lactose, and lactose-free milk gives the moisture and richness with the lactose already broken down.
• Plain sugar. Plain white and confectioners' sugar are low-FODMAP, so the cake and buttercream stay sweet without honey, agave, or polyol sweeteners.

Storage

Keep the frosted cake covered at room temperature for up to 2 days, or refrigerate for up to 5 days and let slices come back to room temperature before serving. Unfrosted layers freeze well: wrap tightly and freeze for up to 3 months, then thaw at room temperature before frosting. Portions of any sweet add up quickly. If you are still in the elimination phase, look up any ingredient in the FODMAP Foods app to see how its rating changes with portion size.