A surprising combination, the syrup adds a lovely balance to the salty cheese.
1. Place oil in a medium saucepan. Add onion, cover, and place over medium heat. Cook, stirring occasionally, 12 to 15 minutes, until onion is soft and starting to brown. Reduce heat to medium-low if they are browning too much before softening. Stir in vinegar and thyme, cover, remove from heat, and set aside while you prepare the pizza.
2. Place a rack in the bottom position of the oven. Preheat oven to 450°F. Coat a large rimmed baking sheet with nonstick cooking spray and sprinkle with cornmeal. Dust clean work surface with flour. Roll out dough to the size of the baking sheet and transfer to the sheet.
3. Spread caramelized onions over dough. Top with cheddar and feta. Sprinkle with pepitas, salt, and pepper.
4. Bake, rotating once halfway through, 13 to 16 minutes, until crust is crispy and cheese is bubbling and just starting to turn golden. Remove from oven. Scatter arugula over pizza and drizzle with syrup. Cut into 8 pieces and serve.
Source: The Splendid Table