There are LOTS of good recipes online .... I make sugar-free since I’m low carb. I love the stuff .... have to be careful not to use food as an excuse to eat ketchup!
Recipe for ketchup using two aluminum cans of ingredients.
https://www.genaw.com/lowcarb/evenbetter_heinz_ketchup.html
6 ounce can tomato paste
8 ounce can tomato sauce
1/4 cup plus 3 tablespoons white vinegar
1/4 cup water, or enough to get the right consistency
1/4 cup granular Splenda or equivalent liquid Splenda
1/2 teaspoon salt
1/4 teaspoon onion powder
1/8 teaspoon allspice
1/8 teaspoon ground cloves
1/8 teaspoon cinnamon
1/8 teaspoon garlic powder
Mix all of the ingredients well in a medium saucepan. Cover and simmer for 1 hour. Cool then chill before serving. Keep refrigerated.
Makes 2 cups or about 32 tablespoons