Step 1

Make the savory bun dough: Heat the milk, vegetable oil and sugar in a large saucepan over medium heat until the mixture is warm and the sugar is dissolved, about 2 minutes (do not boil). Set aside to cool to lukewarm. Sprinkle the yeast on top and let sit until it bubbles slightly, about 1 minute.

Step 2

Add 2 cups flour to the yeast mixture and stir until just combined. Cover with a kitchen towel and let rise in a relatively warm place until the dough has doubled in size, about 1 hour.

Step 3

Whisk the baking powder, baking soda, salt and the remaining ¼ cup flour in a small bowl. Add to the dough and stir, then knead with your hands until completely combined and the dough is elastic and not too sticky, about 2 minutes. Use the dough right away or place in a clean bowl, cover with plastic wrap and refrigerate for up to 3 days, punching down the dough if it rises to the top of the bowl.

Step 4

While the dough is rising, make the filling: Mix together the spinach, feta, parmesan, salt, onion powder and pepper in a medium bowl. Set aside.

Step 5

Melt 3 tablespoons butter in a small saucepan and keep warm. On a floured surface, roll out the dough into a 10-by-15-inch rectangle with a long side facing you. Spread the spinach mixture evenly over the dough.

Step 6

Beginning with the long side farthest from you, use both hands to slowly roll the dough toward you, being careful to keep the roll tight (it’s OK if the filling oozes out a bit). When you reach the end, pinch the seam together. Transfer to a cutting board and, with a sharp knife, cut into 12 slices. Brush a 9-inch round cake pan or deep-dish pie pan with about 2 tablespoons of the melted butter. Place the buns cut-side up in the pan. Brush the tops of the buns with the remaining tablespoon of melted butter.

Step 7

Cover the pan with a kitchen towel and let rise at room temperature until puffy and nearly doubled in size, at least 20 minutes. Meanwhile, preheat the oven to 375 ̊.

Step 8

Uncover the buns and bake until golden brown, 20 to 25 minutes. (Don’t allow the buns to become overly brown.) While the buns are baking, melt the remaining 2 tablespoons butter. When the buns come out of the oven, generously drizzle with the butter, getting it all around the edges and over the top.