Preheat oven to 400 degrees F (200 degrees C).
Spiralize the Zucchini (2) to make 2 1/2 cups of zucchini noodles.
In a skillet preheated to medium heat, melt Unsalted Butter (2 tablespoon). Place Yellow Onion (1) into skillet and cook for a few minutes.
Add Salt and Pepper (to taste), Granulated Sugar (1 teaspoon), Worcestershire Sauce (2 teaspoon), and Fresh Thyme (1 teaspoon). Stir and cook for another couple of minutes.
Add Beef Broth (1/4 cup) and cook until onions are golden brown about 12 minutes. Make sure to stir occasionally to keep the onions from burning.
Next, spray an 5 X 8 baking dish with non-stick cooking spray. In a large bowl combine Zucchini Noodles and French onion mixture. Pour the French onion zoodle mixture into the dish and garnish top with Fontina Cheese (1 cup).
Place in the oven and bake for about 20 to 25 minutes or until golden brown. Remove from oven and cool slighlty before serving. Garnish with fresh thyme if desired.