Add the basil, garlic, tahini, lemon zest and juice, salt, and pepper to a blending container or small blender. Mix until the basil has broken down. Note that it won't be fully smooth.
20 grams (¾ cup) fresh basil, 1 clove garlic, 1 tablespoon tahini, Zest of a lemon, 3 tablespoons lemon juice, ¼ teaspoon sea salt, ¼ teaspoon black pepper
Pour the olive oil into the pesto in a slow stream while blending, until fully incorporated and the vinaigrette is smooth. There should be no visible oil once fully mixed.
100 ml (~⅓ cup) olive oil
Pesto vinaigrette tastes best when served immediately but can be refrigerated in a sealed jar for up to three days.
Notes
Use the stalks: if you're buying a bunch of cut basil to use here, toss the stalks in as well as the leaves. They'll blend right in and you can avoid some food waste without sacrificing flavour.
Harvest from the tops: if you're growing your own basil, harvest individual large leaves and the tops of your plants to encourage more growth and bushier basil plants.
Use fresh basil: if you have your own basil plants, make the pesto dressing immediately after harvesting, within minutes. The longer basil sits, the less flavour it will have. For store bought, try to perk it up in a bit of water before using (cut the ends off, place the cut ends in a glass with fresh water, and give it a couple hours).