Bring a pot of water to boil, make an "x" on the bottom of each tomato. I suggest prepping all the tomatoes at one time and then 3-4 at a time drop them into the boiling water. After about 30 seconds remove the tomatoes and add to ice water. After they have cooled start removing the skins and cores. Cut into quarters and "de-seed".
In a dutch over add ¼ cup olive oil and 3 peeled and crushed and minced garlic cloves. Cook on medium heat until the garlic browns. Add onions and brown. Next add green peppers and diced tomatoes, cook over medium heat. Add oregano leaves (whole) and continue to cook until desired constancy. Add 1 can of tomato paste and optional zucchini. Continue to cook until desired consistency (my family likes chunky marinara).
How to make Homemade Marinara https://www.stockpilingmoms.com/how-to-make-homemade-marinara/