In large saucepan, heat oil over medium high heat.
Add onions and cook until translucent, about 2 minutes.
Add garlic and cook for another minute.
Add Italian seasoning and tomato paste and cook for a minute before adding tomatoes and hot pepper flakes. Bring to boil then reduce heat to low and let simmer, without lid, for 15 minutes. Keeping it uncovered lets liquid evaporate more quickly. Stir occasionally.
Taste and add salt and pepper accordingly. Taste and adjust further as needed - more hot pepper flakes, Italian seasoning or other seasoning as desired.
If desired, use immersion blender to puree chunks a little - be careful not to overprocess. If time permits, simmer on low for another 5-10 minutes, taste and adjust seasoning and serve.
Video
Notes
Use whatever type of canned tomatoes you have. If tomato pieces are too large, chop to desired size with knife or an immersion blender. In place of Italian Seasoning use 1tsp basil, 1 tsp oregano, 1/2 tsp thyme and 1/2 tsp parsley. If too acidic
add 1/2 tsp sugar
add 1/2 tsp baking soda
If too runny
add 1/2 cup of pasta water and simmer for 5 minutes to allow starch to mix with sauce
simmer longer to evaporate more liquid, the longer it cooks, the thicker and more flavourful it will become