Preheat your oven to 350°F (175°C). Line a 12-cup muffin tin with paper liners or lightly grease with oil or butter.
In a large bowl, whisk together 2 cups almond flour, 2 tablespoons coconut flour, 2 teaspoons baking powder, 1/4 teaspoon salt, and 1 teaspoon cinnamon.
In a separate bowl, whisk 3 large eggs, 1/2 cup granulated keto sweetener, 1/3 cup melted butter or coconut oil, 1/3 cup unsweetened almond milk, 2 teaspoons banana extract, and 1 teaspoon vanilla extract until smooth.
Pour the wet ingredients into the dry ingredients. Stir with a spatula until just combined.
The batter should be thick but scoopable. If it looks dry, add 1–2 more tablespoons of almond milk.
Fold in any optional add-ins: 1/2 cup chopped nuts or 1/3 cup sugar-free chocolate chips.
Divide the batter evenly among the muffin cups, filling each about 3/4 full.
Bake for 18–22 minutes, or until the tops are set and a toothpick inserted in the center comes out clean or with a few moist crumbs.
Cool in the pan for 5 minutes, then transfer to a wire rack to cool completely. This helps them firm up and prevents crumbling.