Preheat oven to 350ºF and line a 9-inch round cake pan with parchment paper. Spray parchment paper and sides of the pan with cooking spray.
Add coconut sugar to a high-speed blender or food processor and blend until fine. In a medium mixing bowl, stir together almond flour, baking powder, Pique tea crystals, turmeric, and sea salt. Set aside.
In a large mixing bowl, use a hand mixer to beat together butter and coconut sugar. Add eggs, Greek yogurt, lemon juice, lemon zest, and vanilla extract. Beat until just combined.
Gradually mix dry ingredients into wet until batter is thoroughly moistened. Use a spatula to spread the cake batter evenly in pan. Gently place slices of lemon on top of the cake. Bake for 50-60 minutes or until a toothpick inserted in the center comes out mostly clean.
Cool in pan for 20 minutes. Invert onto a plate and then right side up onto a cooling rack. Cool for 30 minutes before slicing. Serve slightly warm.