Grilled Zucchini Parmigiana

Lightly coat zucchini slices with cooking spray on one side; season with salt and black pepper. Working in batches, grill zucchini on rack of a covered grill over high heat on coated side 4 to 8 minutes or until char marks form; remove. Set aside. Preheat oven to 375°F. Butter a 13×9-inch or 3-qt. rectangular baking dish.

For white sauce: In a medium saucepan melt butter and cook onion over medium heat 5 minutes or until softened. Add flour; cook 3 minutes or until light golden brown, stirring constantly. Add milk, whisking to combine well; bring to boiling. Reduce heat; simmer 2 minutes, stirring often. Stir in basil, nutmeg, 1/2 tsp. salt, and 1/4 tsp. black pepper. Remove from heat.

Layer a third of white sauce, a third of zucchini slices (grill marks up), and half each of mozzarella and Parmesan; repeat layers. Top with remaining sauce and zucchini slices (grill marks up).

Bake, uncovered, 30 to 40 minutes or until bubbling and nicely browned. Remove; let stand 20 minutes. Top with additional fresh basil and flaky sea salt.

*TIP: Ideally, you want zucchini about 9 inches long to cover the width of the baking dish.