1. Preheat the oven to 375°F. In a small ovenproof sauté pan, lightly coat diced onions and thyme leaves with a pinch of salt and olive oil. Put the pan in the oven to roast, stirring occasionally, until the onion is cooked and golden, about 30 minutes.
2. While the onion is roasting, wash and drain the broccoli raab, remove the heavy stems, and roughly chop the leaves and sprouts, about 2 cups worth. Peel and finely chop the garlic. Heat a large sauté pan and coat it with olive oil. Add the broccoli raab, season with salt, pepper, and the hot pepper flakes, and fry over high heat until the broccoli raab is tender. Add the garlic and fry, tossing, for a few seconds.
3. When the onions are done, take them out of the oven and turn the heat up to 450° to 500°F. Roll out pizza dough into a shape 12- to 14-inch diameter onto the back of a a lightly floured baking sheet. Lightly brush the dough with olive oil, leave a 1/2-inch boarder dry. Evenly sprinkle the cheese, braccoli rabe, and the olives. Drizzle about 1 tablespoon olive oil over the pizza. Bake pizza in oven 5 to 10 minutes, until the crust is brown and crisp. Remove the pizza from the oven, sprinkle a few drops of lemon juice on it, slice and serve.