Coarsely chop the sun-dried tomatos and put them in the bowl of a food processor. Add ¾ cup (180ml) of the oil, chopped walnuts, Parmesan, garlic, rosemary, red pepper flakes, salt, and a few drops of lemon juice.
Pulse in the food processor until it's a cohesive paste. Taste and add some or all of the remaining ¼ cup (60ml) oil, additional salt, chopped rosemary, or lemon juice, if desired.
