Add basil, cashews, garlic, and salt to blender or food processor and blend until thoroughly combined.
With blender or food processor on, slowly add olive oil and lemon juice until well combined. Add the Parmesan and blend for 10 more seconds until just combined.
Store for up to 1 week in an airtight container in the fridge.
Notes
Toast the cashews which adds a rich, roasted flavor to the pesto.
If you want a thinner pesto, add 1 tablespoon of olive oil or water at a time.
Use freshly squeezed lemon juice as it tastes better and is cheaper. No store-bought bottle.
If you don't want your pesto to turn brown, pour a small layer of olive oil over top and store in an airtight container in the fridge for one week. You can also freeze for up to 3 months.