Preheat the oven to 350 degrees F (175 degrees C). Grease a 9-inch round cake pan.

Blend garbanzo beans, sugar, egg yolks, lemon zest, 1/2 lemon juice, lemon juice concentrate, orange extract, and vanilla extract together in a food processor until smooth. Stir baking powder into bean mixture.

Whip egg whites together in a bowl using an electric mixer or a whisk until stiff. Fold bean mixture into egg whites. Gently pour batter into the prepared cake pan.

Bake in the preheated oven until a toothpick inserted into the center comes out clean, 40 to 50 minutes. Let cool 20 minutes, then carefully run a knife along the bottom of the pan to release cake and turn onto a wire rack to cool completely.

While cake finishes cooling, heat sugar, margarine, lemon juice concentrate, and lemon juice in a saucepan over medium heat until fully combined, about 2 minutes. Drizzle glaze over cooled cake.