Prepare the pizza dough and set it aside to rise. You’ll need half of the dough for this recipe. The other half can be refrigerated, frozen, or used to make a second pizza.

Lightly oil a large baking sheet and dust it with cornmeal.

Melt the butter in a large skillet. Add the onions and cook them over medium heat for about 12 minutes, until golden, stirring often. Salt and pepper the onions lightly and remove from the heat.

When your dough has doubled and you’re ready to bake the pizza, preheat the oven to 450°F (230°C). Punch the dough down and knead for 1 minute on a lightly floured surface. Divide the dough in half. (Save half for another use.) Shape the dough into a ball. Cover loosely with plastic wrap and let it rest for 10 minutes on a lightly floured surface.

Once it has rested, press or roll the dough into a large, thin circle or oblong. Transfer to the baking sheet and let it rest for 10 minutes.

Spread the tomato jam over the surface of the dough, leaving a 1/2-inch border all around. Drizzle with 1 to 2 tablespoons of olive oil. Distribute the onions evenly over the jam. Top with the cheese. Bake the pizza for 20 to 22 minutes, until the edge has browned and the cheese has blistered. Slide the pizza onto a rack and cool for 5 to 10 minutes before serving. Refrigerate leftovers. Reheat slices directly on a baking sheet, in a 300°F (150°C) oven, for 8 to 10 minutes.