Simple Vegetarian Skillet Lasagna

Name: Simple Vegetarian Skillet Lasagna
Ingredients: 2 Tbs. extra-virgin olive oil; 1 zucchini, chopped; 8 oz. (250 g) button mushrooms, finely chopped; 1 red bell pepper, seeded and chopped; Kosher salt and freshly ground black pepper; 2 garlic cloves, minced or grated; 1 jar roasted garlic or tomato-basil pasta sauce; 1 cup (8 fl. oz./250 ml) milk; Pinch of red pepper flakes; 1/2 cup (4 oz./125 g) oil-packed sun-dried tomatoes, drained; 1/2 cup (3 1/2 oz./105 g) green lentils, rinsed; 1/4 cup (2 fl. oz./60 ml) water; 6 oz. (185 g) no-boil lasagna noodles; 2 cups (2 oz./60 g) fresh spinach; 1 cup (1 oz./30 g) fresh basil leaves; 8 oz. (250 g) mozzarella cheese, sliced; 4 oz. (125 g) provolone cheese, shredded; 1/3 cup (1 1/4 oz./40 g) grated Parmesan cheese, plus more for serving; Basil pesto for serving (optional)