Toast the cashews in a single layer in a skillet over medium heat until fragrant and lightly browned, about 3 to 5 minutes. Stir frequently, and be careful not to burn them.
Wash the ramps under cold water. Use your fingers to scrub off any dirt. Pat dry.
Trim off the very bottom of the roots, being careful not to trim too much of the bulb (it's very flavorful). Roughly chop the white bulbs, red/pink parts, and the ramp leaves.
In a food processor fitted with the S-blade or high-powered blender, combine the cashews, ramps, parmesan, lemon juice, and olive oil. Pulse or blend until smooth and creamy and no visible or overly large pieces of cashew remain, about 60 seconds. Stop to scrape down the sides and add more olive oil in small amounts as needed to promote blending.
Taste the pesto and adjust seasonings as desired. Add more lemon juice, salt, and pepper if preferred.
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Notes
Storage: Store in an airtight container in the fridge for up to one week, or in freezer-safe containers in the freezer for up to 3 months for later use. Put a squeeze of lemon juice and drizzle of oil on top of the pesto before storing to help prevent browning.
Creative ways to use ramp pesto: Pasta sauce, sandwich spread, as a dip, on top of roasted vegetables or grilled meats and salmon, mixed into eggs, and as a base for salad dressings.