Toast pine nuts in 350°F oven, or toaster oven, for 3 to 4 minutes. Set aside.
Set a medium saucepan with salted water to boil. Once at a boil, cook spaghetti until al dente - about 7 to 8 minutes - or by package instructions. If cooking in advance, lightly oil to prevent clumping while it cools.
In a food processor, add pine nuts, garlic cloves and basil. Pulse 10 to 15 times. Add parmesan, lemon zest, ¼ cup ricotta cheese and salt. Turn the food processor to 'On.'
With food processor running, slowly add olive oil and blend for 1 minute.
In a large sauce pan, add cooked spaghetti and creamy lemon ricotta pesto. Sauté over low heat until pasta is evenly coated. Plate and top with remaining ¼ cup of ricotta cheese.