Preheat your oven to 350°F (175°C). Grease a 9-inch round cake pan.
Combine dry cake ingredients: In a large mixing bowl, whisk together 2 cups almond flour, 1/4 cup coconut flour, 1/2 cup coconut sugar, 1 tsp baking soda, and 1/4 tsp salt.
Mix wet cake ingredients: In a medium bowl, whisk together 1/2 cup melted coconut oil, 4 large eggs, 1/2 cup almond milk, 1 tbsp apple cider vinegar, and 2 tsp vanilla extract until smooth.
Combine cake batter: Pour the wet ingredients into the dry ingredients. Stir with a spatula until just combined.
Prepare streusel topping: In a small bowl, mix 1/2 cup almond flour, 1/4 cup coconut flour, 1/4 cup coconut sugar, 1/4 cup chopped pecans (if using), 1/4 cup melted coconut oil, and 1 tsp cinnamon until crumbly.
Assemble cake: Pour the batter into the greased cake pan, smoothing the top with your spatula. Sprinkle the streusel topping evenly over the batter.
Bake: Place in the preheated oven and bake for 30 minutes, or until a toothpick inserted into the center comes out clean.
Cool and enjoy: Let the cake cool in the pan for 10 minutes before transferring to a wire rack to cool completely. Slice and savor with your favorite coffee.