Rinse the orange and pat it dry. Zest the orange and set the zest aside. Cut the orange in half.
In a liquid measuring cup, squeeze half an orange until you have ¼ cup of orange juice. (Use another orange half if needed.)
Add the olive oil, vinegar, zest salt, garlic powder and pepper. Whisk to combine. Use the vinaigrette on salads or vegetables and refrigerate it within two hours.
Store leftover orange dressing in a sealed container in the refrigerator for up to one week. (See notes.)
Notes
The oil will rise to the top and solidify during refrigeration. You can run the jar under very warm water and whisk the vinaigrette to emulsify it again. Or, let the dressing sit at room temperature for 30 minutes before whisking it or shaking the jar.