Grease a 9x13 baking dish with cooking spray and spread 1 cup of marinara sauce on the bottom of the dish; set aside.
Cut the zucchini in half, lengthwise, and scoop out the flesh with the tip of a spoon. Arrange the zucchini boats in the baking dish, flesh-side UP; sprinkle salt over each boat and set aside.
Prepare the Taco Beef mixture.
Once you've cooked the beef, wipe down the zucchini boats with paper towels. Fill the boats with the prepared beef mixture—no specific amount – just spoon in what the zucchini will hold.
Top each zucchini boat with remaining marinara sauce and add cheese on top.
Bake for 25 minutes or until the zucchini is tender and the mixture is bubbly.
Nutritional info is an estimate and provided as courtesy. Values may vary according to the ingredients and tools used. Please use your preferred nutritional calculator for more detailed info.