Whisk Greek yogurt, lemon juice, Dijon, honey, grated garlic, onion powder, salt and pepper in a medium bowl until completely smooth.
Pour in olive oil in a thin stream while whisking continuously. Whisk 30 seconds more, until glossy with no oil pooling at the edge.
Whisk in 2 tablespoons cold water, one tablespoon at a time. Add more water only 1 teaspoon at a time until the dressing pours in a steady ribbon.
Let the dressing stand 5 minutes, then whisk again so the garlic and seasonings distribute fully.
Add salt by the pinch, lemon by the teaspoon or honey by the half-teaspoon as needed. Serve immediately or chill and readjust with water before using.
