I got this recipe from the Food Network and it is a great simple recipe for when you don't have a jar of marinara sauce lying around. Excuse the lame photo - I only had my phone :)
Simple Marinara Sauce
1/4 cup olive oil
1/4 medium onions, diced
4 cloves garlic, crushed
3x 28oz cans chopped tomatoes (I used fresh tomatoes)
1/2 cup fresh chopped garlic
2 tsp salt
black pepper to taste
Heat oil in a medium saucepan on a medium-low heat.
Fry onion and garlic until onion is browning.
Add tomatoes, basil, salt & pepper.
Bring to boil and reduce heat to low and heat uncovered for 25-30 minutes until thickened.
Serve same day or freeze.