Orecchiette with Lentils, Onions, and Spinach

INGREDIENTS

• 1/3 cup olive oil
• 3 large onions (2 pounds total), thinly sliced (7 cups)
• 2 garlic cloves, chopped
• 1/4 teaspoon salt
• 1/8 teaspoon black pepper
• 1 Turkish or 1/2 California bay leaf
• 1 cup French green lentils
• 1 pound orecchiette, fusilli, or penne
• 2 (5-ounce) bags baby spinach
• 1 1/2 ounces finely grated Parmigiano-Reggiano (3/4 cup plus 2 tablespoons)