Finely chop the almonds in a food processor for about one minute.
Include the garlic in the food processor and continue blending for an additional 10 seconds.
Now, add the basil, Parmesan cheese, lemon zest, lemon juice, salt, and pepper to the food processor. Blend everything for another 10 seconds. While the processor is still running, gradually pour the olive oil into the mixture in a slow and steady stream.
Using a spatula, scrape down the sides of the bowl after adding all the olive oil. Then, process the mixture once again until it becomes almost smooth.
If you prefer a thicker pesto, you can stop at this point. However, if you prefer a thinner consistency, you can add up to ¼ cup more olive oil, adjusting it according to your preference.
Transfer the pesto into a jar that has a lid and store it in the refrigerator until you are ready to use it.