• Crushed red pepper, for serving
Preheat oven with pizza stone to 500 degrees. (If you don't have a pizza stone, you can use a baking sheet.)
In skillet, heat 2 tablespoons olive oil over medium heat. Add onion and pinch of salt and cook, stirring often, until browned and caramelized, about 30 to 40 minutes. Stir in sage and cook for 2 more minutes. Remove from heat.
Divide pizza dough in half. On floured pizza peel or baking sheet, flatten out half the dough into a 10-inch round. Top with half of the ricotta, half of the Parmesan, a good pinch of salt and few turns of pepper, half the onion, and half the squash shavings. Brush squash with thin, even layer of olive oil and sprinkle with salt and pepper.
Bake until crust and squash are lightly browned. Begin checking doneness at 8 minutes. Repeat with other half of ingredients.