Using a food processer, add the peppers and onions in batches until finely chopped.
In a large stock pot, heat the olive oil. Then add the onions and pepper mixture. Sauté the vegetables until soft. Stir in the tomato paste, brown sugar, garlic, salt, oregano, bay leaves and basil.
Add the tomatoes and stir to combine.
Bring the ingredients to a boil. Once boiling, reduce heat and simmer, uncovered, for 4 hours, make sure to stir every 15 minutes or so. Remove and discard the bay leaves.
Sterilize the mason jars and lids in a hot water bath.
For each quart jar you will be using, add 2 tablespoons of lemon juice.
Ladle the marinara sauce into the mason jars, leaving ½-inch headspace at the top; wipe the rims.
Place a sterilized lid on top and screw until tight.
Place the sealed jars in the stock pot filled with water that's a couple of inches above the jars.
Bring the water to a rolling boil and boil for 40 minutes.
Remove the jars and allow them to cool down before storing. While the jars cool, you'll hear the seals of the jar lids "popping." You'll know you've done a great job!