Preheat oven to 400 degrees F.

Cut spaghetti squashes in half lengthwise and scrape out the seeds.

Place squash cut side down on a baking tray.

Roast for 35-45 minutes, until squash is tender.

While squash roasts, heat 2 tablespoons olive oil in a saucepan over medium heat.

Add minced onion and a pinch of salt.

Cook onions for 10-15 minutes, stirring frequently until tender.

Add minced garlic, red pepper flakes, and another pinch of salt.

Stir until garlic is fragrant (about 30 seconds).

Add whole tomatoes and their juices, crushing the tomatoes with your hands.

Season with additional salt, pepper, and sugar (optional).

Add 1/4 cup minced basil and parsley.

Simmer the sauce while squash finishes roasting.

When squash is cool enough to handle, scrape the flesh out into strands.

Layer about 1/2 cup sauce in the bottom of each squash shell.

Layer some squash strands, a handful of mozzarella and asiago cheese, extra basil, and more sauce.

Repeat layers until the squash shells are filled (about 3 layers).

Top each boat with a generous amount of mozzarella and asiago.

Bake for 20-25 minutes.

Broil for a few minutes on high to brown the cheese, watching carefully to prevent burning.

Allow to rest for 10 minutes.

Drain excess moisture by carefully tipping the boats over the sink.

Serve.