1. Place an oven rack in the lowest position. Preheat the oven to 450 degrees . Brush a rimmed baking sheet with 2 teaspoons oil and sprinkle with cornmeal. Roll out dough to size of prepared baking sheet and transfer to sheet.
2. Brush remaining oil on dough and scatter onion, cheddar, sausage and walnuts over it.
3. Bake pizza until bottom is crisp and starting to brown and cheese is melted and bubbling, 13 to 17 minutes. Drizzle with maple syrup and top with field greens.