I use tomato paste all the time. Sometimes I need up to half a cup, sometimes just a little bit. When I make my own, I can store it in the sizes I tend to need most, so I have no more partly used cans in the fridge.
The hardest part of the process is squishing the tomatoes, separating the pulp from the skin and seeds. I use the fruit strainer attachment to my KitchenAid stand mixer, but you can use a hand-crank version, as I did for years. If you process a lot of tomatoes – and I do – a motorized strainer is a blessing.
I make tomato paste the easy way: I roast it in a wide flat pan until the consistency is just right. I like to keep some in small (4-ounce) jars, and some I’ll freeze into tomato paste cubes, which are perfect when you need just a spoonful.