Using a potato masher, mash some of the tomatoes so there is liquid in the bottom of the pot.
Add chopped onions, peeled garlic, and seeded and chopped hot peppers if using.
Bring to a boil, stirring frequently so it doesn't stick.
Reduce heat and simmer for 30 minutes. Don't cover the pot so it can start to reduce.
Remove from heat and let cool for about 10 minutes.
In batches, place in a blender and puree.
If you want to remove the seeds, pour into a food mill and press into a clean stockpot.
Return to a boil and reduce to a simmer.
Simmer until it is the consistency that you want.
Add chili powder and salt. If you like to heat things up, you can add any peppers that you want at this time. Adjust seasonings to taste.
Put in pint jars and process at 6 pounds pressure for 20 minutes. Remember to adjust for your altitude.
Notes
This enchilada sauce can be canned or frozen. If you don't add the chili powder, it makes a great tomato soup.As written, this recipe needs to be pressure canned. To use a waterbath canner, add 1 Tbsp bottled lemon juice to each pint jar before filling with sauce. Then process for 35 minutes.