Step 1

Cover a work surface with a silicone baking mat or a large piece of parchment paper. In a medium bowl, whisk together the coconut flour, baking powder, and xanthan gum. Set aside.

Step 2

In a large, microwave-safe bowl, heat the cheese on high in 30-second increments until almost liquid. Stir in the flour mixture and eggs and knead in the bowl using a rubber spatula.

Step 3

Turn the dough out onto the prepared work surface and continue to knead until cohesive. Set dough aside while preparing the filling.

Step 4

Preheat the oven to 375°F and line a baking sheet with a silicone baking mat or parchment paper.

Step 5

Squeeze out as much moisture from the spinach as possible and place the spinach in a medium bowl. Stir in the feta, Parmesan, garlic, marjoram, salt, and pepper until well combined.

Step 6

Lightly grease another baking mat or large piece of parchment paper and transfer the prepared dough onto it. Pat into a rough square and top with another piece of parchment or waxed paper.

Step 7

Roll out the dough to a 16-inch square. Spread the filling on top, leaving a 1/2-inch border. Roll up the dough tightly and pinch the seam to seal.

Step 8

Use a very sharp knife to cut the dough into 1-inch slices and place the pinwheels cut side down on the prepared baking sheet. Brush with the butter and sprinkle with a little coarse salt.

Step 9

Bake for 18 to 22 minutes, until the pinwheels are golden brown and just firm to the touch. Remove from the oven and let cool completely on the pan.