Heat the oven to 350°F and line a baking sheet with parchment. Whisk the almond flour, coconut flour, baking powder, and sea salt together.
Beat the softened butter and allulose until creamy, then beat in the egg, vanilla, and lemon zest. Stir in the dry ingredients just until combined.
Fold the blueberries into the dough gently so most remain whole. Divide the dough into 12 rounded mounds and place them 2 inches apart on the pan.
Rub the almond flour, brown monk fruit sweetener, butter, and cinnamon together with your fingertips until moist crumbs form.
Press a generous pinch of streusel onto each cookie and lightly flatten the tops. Bake for 13 to 15 minutes, until the edges are lightly golden and the centers are set.
Cool on the baking sheet for 15 minutes before moving the cookies. The extra cooling time gives them a tender muffin-top center without falling apart.