Preheat oven to 390 degrees. In a large bowl, sift together the flour, baking powder, sugar, and salt. Make a well in the center of flour mixture and place buttermilk in the well and mix to form a soft dough. Turn dough onto a floured surface and knead until smooth. Roll out to a 12” square. Place the tomato sauce and oregano in a bowl and mix to combine.
Spread the tomato sauce mixture over the dough and sprinkle with spinach and cheese. Roll to enclose the filling. Slice the roll into 9 to 10 pieces and place side-by-side in a lightly greased 8×8 pan lined with parchment paper. You can sprinkle with additional cheese if you like.