A while before you want to eat, take the spiralized zucchini noodles, salt them generously, and place them in a strainer over a bowl. Place in the refrigerator for at least 30 minutes.
Meanwhile, to make the avocado pesto, combine the avocado, basil, miso, olive oil, lemon juice, and garlic in a blender or food processor until smooth. Add (plenty of) salt, pepper, and nutritional yeast (if using) to taste.
Rinse the zoodles, squeeze them very gently to remove excess liquid without breaking them, and pat them with a clean towel to dry the surface.
Fold the avocado pesto into the zucchini noodles. Also fold in the cherry tomatoes if using. Serve cold, as soon as possible. These avocado pesto zucchini noodles really taste best when eaten within 2 hours or so of being prepared, but if necessary, keep leftovers in the refrigerator in a loosely-covered container for up to 24 hours.
Notes
I recommend also placing the avocado and lemon in the refrigerator a little while before making the avocado pesto, so that the whole dish is nice and cold right when you prepare it.For an even more refreshing variation, substitute a cucumber for 1 or 2 of the zucchini noodles.To make this recipe strictly paleo and/or soy-free, omit the miso and add another umami ingredient (such as chopped sundried tomatoes folded into the sauce), or increase the olive oil to 1 tablespoon.