Prepare your water bath canner, jars and canning lids per manufacturer and USDA canning guidelines.
To puree tomatoes: Blanch, peel, core, and seed tomatoes. Put them into a colander and let them sit for 15 minutes. Discard the liquid. Put the tomatoes into a food processor. Purée with metal blade.
Italian-Style Tomato Sauce (and how to can it!) https://www.thegratefulgirlcooks.com/italian-style-tomato-sauce/