Zucchini, Tomato, and Potato Tian with Caramelized Onions | America's Test Kitchen

Ingredients

• 2 tablespoons extra virgin olive oil
• 3 slices thick-cut bacon, sliced into thin strips
• 3 medium yellow onions, halved and sliced 1/4 inch thick (about 3 cups)
• Salt
• 2 medium garlic cloves, minced or pressed through a garlic press (about 2 teaspoons)
• 1 pound zucchini, trimmed and sliced 1/4 inch thick
• 1 pound russet potatoes, peeled and sliced 1/4 inch thick
• 1 pound plum tomatoes, cored and sliced 1/4 inch thick
• 1 teaspoon minced fresh thyme leaves
• Ground black pepper
• 2 ounces shredded Gruyère cheese (about 1/2 cup)