Soften the dried tomatoes. In a small pot with a lid, bring the water to a boil over high heat. When boiling, add the sun-dried tomatoes, remove from the heat, cover. Set aside for 10 minutes to steep.
Make the pesto. Drain the tomatoes over a bowl, reserving the soaking liquid. Add the plumped tomatoes to a food processor along with the cashews, garlic, oregano, basil, and red pepper flakes (if using). Pulse until the ingredients are finely chopped, pausing once to scrape down sides. Add the cheese and pulse to combine. With the processor running, stream in the olive oil. Stream in the reserved soaking liquid, a spoonful at a time, until you have a spreadable, nearly uniform texture (I use about 1/4 cup in total). Serve immediately, or store in a jar in the refrigerator for up to a week.
This recipe makes enough pesto to combine with 1 pound of pasta (or more, depending on how saucy you like things). To make red pesto pasta:
Cook 1 pound of pasta in boiling salted water. Reserve 1 cup of the pasta's starchy water before draining.
Add the red pesto to a large mixing bowl and loosen with a splash of the reserved pasta water. Then toss with cooked pasta until coated and creamy, adding more pasta water as necessary.
To use oil-packed sun dried tomatoes: Drain them well and skip the step of soaking them in hot water. Add them directly to the food processor. Stream in water in place of the reserved soaking liquid.
To freeze: Transfer to a sealable freezer safe jar and store in your freezer for up to 3 months. Defrost it in the refrigerator before using it.
Feel free to double this pesto. I based the quantity on one cup of dry tomatoes because 4 ounce bags are a common portion size sold at grocery stores. In a standard food processor you could easily double this amount, and use the whole bag from our shop!
To toast your own cashews: Preheat the oven to 350°F. Spread nuts on a baking sheet in a single layer. Toast for 6 to 8 minutes or until fragrant and lightly browned. Remove from the oven and allow to cool. Feel free to swap cashews for pine nuts, walnuts, sunflower seeds, or almonds.