To make the cereal milk, add the milk and ½ cup cereal to a 2 cup measuring cup or bowl. Stir to combine and let the cereal steep for 20 minutes.

After 20 minutes, use a mesh strainer to strain the cereal from the milk and discard the cereal.

Stir the brown sugar and pinch of salt into the milk. Measure out 1 cup of the cereal milk to use in the cake. Any leftover milk can be used to make the frosting.

Preheat oven to 325 degrees. Spray a 9x9 square baking pan with non-stick spray and line with parchment paper.

In a large bowl, whisk together the gluten free flour, cornstarch, xanthan gum, baking powder, salt, and granulated sugar. Set aside.

In a large measuring cup or small bowl, whisk together the prepared cereal milk, oil, and vanilla extract and then set aside.

Add the egg whites and cream of tartar to a medium bowl. Use a hand mixer to beat the egg whites until stiff peaks form then set aside.

Pour the cereal milk mixture into the dry ingredients and mix until just combined, making sure to scrap the bottom of the bowl. Add half of the egg whites to the batter and gently fold the egg whites
in.

When the egg whites are mostly incorporated, add the remaining egg whites. Gently fold the egg whites into the batter until fully incorporated and no white streaks remain.

Pour the cake batter into the prepared pan then sprinkle the Fruity PEBBLES™ cereal evenly over the top of the cake.

Bake at 325 degrees for 30 minutes or until a cake tester comes out clean or with a couple moist crumbs.

Cool the cake on a wire rack completely then frost with Vanilla Buttercream Frosting and decorate the top with additional Fruity PEBBLES™ cereal.