This One Bowl Gluten-Free Birthday Cake could hardly be easier! Deep dark chocolate cake is topped with fluffy buttercream frosting for the perfect birthday treat.
Preheat oven to 350°F. Line the bottom of an 8-inch round cake pan with parchment paper, and grease the paper and sides of the pan.
In a large bowl, use a hand or stand mixer to beat the butter and sugars until fluffy; scrape down bowl. Add the egg, yolk, and vanilla extract, and beat until combined. Add the yogurt and coffee and mix until well combined.
Place a sifter over the bowl and in the teff flour, cocoa, baking soda, baking powder, and salt, then sift it into the bowl.
Beat in the flour mix on low until just combined, and scrape down the bowl a final time.
Pour the batter into the prepared pan and smooth the top using a rubber spatula. Place the cake in the oven and bake for 30-35 minutes, until a toothpick inserted into the center comes out clean and the top is set.
Place the cake on a wire rack to cool for 20 minutes in the pan, then turn out onto the rack to cool completely.
Frost the top with chocolate buttercream frosting.