1. Preheat oven to 450°. Toast walnuts on a baking sheet 3–4 minutes or until fragrant and lightly browned. Transfer immediately to a plate; let cool.
2. Heat 1 teaspoon oil in a nonstick skillet over medium heat; add onion. Cook, stirring occasionally, 6–8 minutes or until onion is soft and golden.
3. Place crust on a baking sheet coated with cooking spray. Top with walnuts, onion, and tomatoes. Season with salt and pepper; arrange goat cheese on top.
4. Bake for 7 minutes or until crust is golden, crisp, and warmed through. Scatter arugula on top, and drizzle with remaining oil. Let cool slightly before cutting into wedges.