Anonymous wrote:How did you make it bitter? Did you accidentally drop a lemon seed in there or something?
I'm surprised it turned out so bad. I eat vegan pesto all the time and even without cheese it's completely delicious (usually they use nutritional yeast but even without you'd still have a tasty garlicky-parsley-nutty paste). Maybe you're just not a good cook.
Low quality olive oil would make it bad.
I also do a lot of vegan pesto and have used pine nuts, walnuts, pistachios, or pumpkin seeds to good results. Almonds are okay, but recommend starting with slivers. Sunflower seeds was not a favorite but that's a personal taste thing. Pecans were delicious to me but it might not be universally appealing since their flavor is really unique.
I rarely use lemon, but I do use excellent extra virgin olive oil.
After making lots of variations of pesto with fresh basil from the garden over the summer, the Costco one just doesn't taste good anymore.