Toast pine nuts in a 350 degree oven until golden brown (about 5 minutes).
Pulse toasted pine nuts, garlic, and parmesan cheese in food processor until a course mixture forms.
Mound basil leaves on top of pine nut mixture. Squeeze lemon over basil.
With food processor running, drizzle olive oil into mixture. The pesto paste should be formed by the time the oil has been fully incorporated.
Add salt to taste and pulse just once or twice more to mix in.
Store in an airtight container with a thin layer of olive oil over the top.