Skillets are known for their ease. Lasagna is known for its complexity. How can two contradictory concepts come together in one meal? Life is a contradiction, my friend. Lean into the confusion, and enjoy the ease of making this meal, with only one pan and one pot dirtied, but flavors that portend intricacy to the highest degree. Two cheeses, a slew of veggies, and garlic bread on the side? The only evaluation you'll need at the end: delicious.
Break up noodles into five to seven pieces per noodle. Pieces don't have to be even.
Once water is boiling, add noodles and cook until al dente, 8-10 minutes.
Reserve ½ cup pasta cooking water. Drain noodles in a colander, then run briefly under cold water to stop cooking the process. Set aside.
While noodles cook, prepare ingredients.
Prepare Ingredients and Cook Vegetables
Trim zucchini ends, halve lengthwise, and cut into ½" dice.
Halve and peel onion. Cut halves into ¼" dice.
Place a medium oven-safe pan over medium-high heat and add 2 tsp. olive oil. Add zucchini and red onion to hot pan. Stir often until lightly browned and tender, 3-5 minutes.
Add spinach and cook until spinach is wilted, 1 minute.
Season with ¼ tsp. salt and a pinch of pepper. Remove from burner. Transfer vegetables to a plate.
Reserve pan; no need to wipe clean.
Make the Sauce
Return pan used to cook vegetables to medium-high heat. Add marinara, cream, reserved pasta water, half the garlic (reserve remaining for garlic bread), ½ tsp. salt, and a pinch of pepper.
Bring to a rolling boil and boil 1 minute. Rolling means more than a few bubbles; a rolling boil means water is boiling vigorously, 20-30 seconds.
Remove from burner.
Assemble the Lasagna
Stir pasta, vegetables, and Parmesan into pan with sauce. Top with mozzarella.
Finish the Dish
Place pan with lasagna in hot oven and bake until mozzarella is bubbly and lightly browned, 10-12 minutes.
Remove from oven and rest 5 minutes.
While lasagna rests, halve French roll and place on prepared baking sheet, cut side up. Spread 1 tsp. olive oil and remaining garlic on rolls.
Bake until bread is golden brown, 5-6 minutes.
Serve family-style. Bon appétit!