Preheat oven to 400 degrees. Spray a baking sheet and an 8” X 8” baking pan with nonstick spray.

Slice off and discard zucchini ends. Cut zucchini in half widthwise, and cut each half lengthwise into 1/4-inch-thick strips.

Evenly lay zucchini on the baking sheet, overlapping if needed. Sprinkle with 1/2 tsp. each garlic powder and onion powder. Bake for 10 minutes.

Meanwhile, bring a large skillet to medium-high heat. Add beef, mushrooms, onion, and remaining 1/2 tsp. each garlic powder and onion powder. Cook and crumble until beef is fully cooked and veggies have softened, 5 - 7 minutes.

Remove skillet from heat, and stir in mustard and cream cheese until uniform.

Flip zucchini. Bake until softened, about 10 more minutes.

Meanwhile, in a medium-large bowl, combine spinach, ricotta cheese, egg, salt, and pepper. Mix until uniform.

Remove sheet from oven, and increase temperature to 425 degrees.

Evenly layer ingredients in the baking pan: half of the sliced zucchini, half of the beef mixture, 1/2 cup crushed tomatoes, 2 lasagna sheets, and half of the spinach mixture. Repeat layering with remaining zucchini, beef, and spinach mixture, followed by remaining 2 lasagna sheets, and remaining 1/2 cup crushed tomatoes.

Top with cheddar. Cover pan with foil. Bake for 30 minutes.

Remove foil and bake until lasagna sheets are cooked through and cheese has lightly browned, 8 - 10 minutes.

Let cool for 10 minutes before slicing.