1. Peel the lemon rinds, being careful not to include much of the white part of the peel as it’s very bitter.
2. In a food processor add almonds and pulse until coarsely chopped. Then, add in lemon rind, sugar, salt, pepper, cheese and pulse until well combined. Then process again while streaming in lemon juice and olive oil. Set aside.
3. In a large pot, bring water to a boil and cook pasta until al dente, reserving at least 1 cup of starchy pasta water.
4. Transfer pasta to a large skillet (or use the same spaghetti pot) and add pesto, butter, juice of 1 lemon and pasta water (as needed). Toss to combine until pasta is well coated. Serve and garnish with additional freshly grated cheese, pepper, and lemon zest (optional).
