You can buy canned tomato puree at a lot of grocery stores. Otherwise just use canned tomatoes and run them through the food processor or blender till smooth. The idea is just plain pureed tomatoes without seasoning.

For extra lusciousness, add a little bit of heavy whipping cream or use whipping cream in place of some of the coconut milk. Light coconut milk can be used but does not yield the same thick and creamy results.

Masala Paste:
2 onions (I used one yellow, one purple, together totaling about 3 cups when chopped)
5 cloves garlic
a 2-inch piece of fresh ginger
3 tablespoon garam masala
1 tablespoon chili powder
1 tablespoon turmeric
1 tablespoon cumin
1 1/2 teaspoons ground cloves
2 teaspoons salt
½ teaspoon cayenne pepper
a small pile of of cilantro stems
a fistful of almonds
juice of one lemon

Run everything through the food processor as-is until mostly smooth (see picture) and you’re done. Make this paste once and keep it in the freezer and you’ve got what you need for 5 ingredient Chicken Tikka Masala FROM SCRATCH for many happy days. Makes about 1 1/2 cups of paste.