
Cut off and discard ends of lemon.
Cut lemon into quarters; remove and discard seeds.
Transfer lemon to a food processor or blender, and process until finely chopped, about 1 minute.
Add oil, herbs, vinegar, mustard, and garlic; process until mostly smooth and well combined, 30 seconds to 1 minute.
Transfer vinaigrette to a small bowl, and whisk in salt and pepper.