Step 1

Position a rack in your oven 6 inches from the broiler and heat broiler on high.

Step 2

Grease a shallow 9x13-inch baking dish or rimmed sheet pan with softened butter.

Step 3

Season zucchini with salt and pepper and arrange on baking pan. Broil just until squash is beginning to soften, about 4 minutes.

Step 4

While squash bakes, whisk together cream, thyme, garlic powder, parmesan cheese, and flour in a small bowl. Pour mixture evenly over squash, then top with Gruyere cheese and panko breadcrumbs.

Step 5

Return to oven and broil until golden brown and bubbly, 4-5 minutes. Enjoy!