Press or mince garlic finely. Add to food processor with egg, lemon juice and zest. Pulse to combine well, then with processor running, drizzle oil into feed tube very slowly. Mix will emulsify into a mayonnaise consistency. Taste and season with salt and pepper, pulsing to combine. May be thinned with additional lemon juice if desired. Refrigerate for at least 30 minutes before serving. Best if used within 24 hours.