Preheat oven to 350. Lightly drizzle a 9x13 pan with olive oil.
Cut zucchinis in half length-wise and carefully scoop out the insides so you're left with a boat of zucchini that's around 1/4" thick on all sides. Lightly sprinkle with sea salt and set in prepared pan. This will draw out the moisture so you don't have soggy zucchini boats.
In a large skillet set to medium, heat olive oil. Once hot, sauce onions and peppers for about 10 minutes or until onions begin to brown and caramelize. Season with salt and pepper. Add mushrooms and stir. Cook until liquids release, about 4 minutes.
Add minced garlic and Italian seasoning. Cook for 30 seconds or until fragrant. Remove from heat.
With a paper towel or napkin, wipe out salt and water from zucchini boats.
Assemble boats by spreading about 2 Tablespoons of your favorite pasta sauce in the bottom of each zucchini. Then add 2 Tablespoons of the pepper and mushroom mix into the boats. Top with tomato halves, olives, and pepperoncinis.
Bake for 30 minutes or until warmed through and tomatoes have burst.
Top with freshly chopped basil.
Enjoy!