UPSIDE-DOWN PEPPERONI AND CHEESE FOCACCIA

Steps:

• Place the flour, sugar, salt and yeast in the bowl of a stand mixer fitted with the dough hook. Combine the warm water and 3 tablespoons of the olive oil in a liquid measuring cup. Turn the mixer to low and add the warm-water mixture to the dry ingredients, mixing until a loose ball forms, 1 to 2 minutes. (Alternately, do this by hand: Combine the dry ingredients in a large bowl. Make a well in the center, then add the warm water and oil and stir with a wooden spoon.)
• Increase the speed to medium-high and knead the dough until smooth and slightly tacky but not sticky, about 7 minutes. (If using your hands, gather the dough into a ball, turn it out onto a floured surface and knead, dusting your hands and the surface as needed with flour, about 5 minutes.)
• Pour 2 tablespoons of the olive oil into a large bowl, using your hands to coat the inside completely. Pour the remaining 1/3 cup plus 1 tablespoon olive oil into an 11-by-17-inch rimmed baking sheet, tilting and swirling to coat it with oil. Cover the bottom of the oiled pan with a single layer of the pepperoni, then crush and sprinkle the dried oregano evenly over the pepperoni. Using oiled hands, divide the dough in half, placing half into the oiled bowl, turning once to coat. Place the other half into the prepared pan, spreading gently with your hands. (Dough will not completely cover the pepperoni at the point; you will stretch it further later.) Dip a pastry brush in the oil on the baking sheet and brush oil over surface of dough. Cover both the baking sheet and bowl of dough loosely with plastic wrap and let rise in a warm place until the dough fills about two-thirds of the baking sheet and the dough in the bowl doubles in volume, 1 to 1 1/2 hours.
• Remove plastic wrap from the baking sheet and bowl. Gently using your hands, press and stretch the dough to completely cover the bottom of the pan evenly, doing your best to keep the pepperoni in a single layer. Sprinkle mozzarella in an even layer over the dough. Using oiled hands, remove the dough from the bowl and stretch and gently press into an even layer over top of the mozzarella. Pour any remaining oil from the bowl over top of the dough and use a pastry brush to brush evenly over the surface. Cover loosely with plastic wrap and let rise in a warm place until doubled in volume and extremely puffy, 1 to 1 1/2 hours.
• Meanwhile, position a rack in the middle of the oven and preheat to 500 degrees F.
• Bake until the top is deep golden brown, bread has pulled away from sides of baking sheet and oil is sizzling around the edges, 15 to 20 minutes. Remove from the oven. Let cool for a few minutes before inverting onto a cutting board. Cut into squares with a pizza cutter and serve with warm marinara sauce for dipping.