Cut plum tomatoes in half. Place tomatoes cut side down on a parchment lined baking sheet.
Add 1/4 cup chopped basil, 2-3 garlic cloves, 1/2 teaspoon kosher salt, and 1/4 teaspoon cracked pepper to each tray. (Adjust to the number of trays you can make with your tomatoes.)
Drizzle olive oil or grapeseed oil over tomatoes.
Roast in oven for 30 minutes, then rotate if more than one tray is in the oven. Return to oven and cook for another 30 minutes.
Let cool slightly, then using tongs, peel off the skins.
Add tomatoes and herbs to a food processor and pulse a few times to desired consistency.
Label and store in refrigerator for up to 5 days, freeze, or can by cooking in a water bath for 40 minutes.