Homemade Ketchup

makes 4 cups

5 lbs fresh tomatoes
2 lb onions- chopped- use sweet onions- yellow onions
4 tablespoons evoo extra virgin olive oil
4 tablespoons tomato paste
1 cup apple cider vinegar
dash of paprika 
1/3 cup splenda brown sugar- - have also used 1/8 cup  pure honey instead-can also use agave sugar- I am still learning measurements with that (one time I used maple syrup- improvise)
clove of garlic is also optional too 
several dashes -dash of salt to taste 
if you want it spicy a jalepeno pepper or tabasco sauce
can also add garlic and a - see its all what I have in the kitchen 

chop up the onion and stick in skillet- brown it on up..meanwhile take the tomatoes and blend em up and make em a soup- now some will use canned tomatoes if you do reserve the juice to make it thicker. blend in all the other ingredients and add the onions- smoothing it out-   If you want it spicy -now is when you add the tabasco or the pepper and blend more. Pour back into onion pan- bring to a boil until its all and simmer for about an hour- now you can also do it in a crockpot but takes a few hours to let it soften and simmer. 
Pour into a sealed container or containers and let chill overnight to get tasty. Should last at least 1  month- have had larger batches last up to 2 months- is freezeable too if you want to use as sauce for sloppy joes, etc.  I am not an expert, I just cook and eat and feed my kids healthy choices.
Some say its not salty enough, I like it so my kids get their vegies and its alot healthier and cheaper  then bottled ketchup.

Make sure you use real olive oil and sweet onions- vidalia onions make it sweeter. yes the recipe can be halved. Yes I have used this recipe for  almost  20 years in one form or another..if its not sweet enough for you- use more splenda brown sugar or whatever sweetener you are using- splenda brown sugar makes it taste the best.  I hope I did not forget anything as I keep it in my brain and have not written it out in many years.

I add more spices when I need a bbq, I add peppers, hot, or tabsaco- have even added maple syrup, and other things.   I used a huge gallon drinking jug for the ketchup that pours and refill a jar as it empties out.

recipe source here