In a jar or small bowl, whisk together all of the ingredients until fully blended. Sometimes, if your mustard is cold, it will need a few minutes to warm up before it fully incorporates.
2
Taste, and adjust if necessary—for more tartness, add another teaspoon of apple cider vinegar, or for more sweetness/balance, add another teaspoon or two of maple syrup (I usually add one).
3
This salad dressing will keep well in the refrigerator for up to 10 days. Real olive oil can solidify slightly when cold; if that happens, simple let it warm to room temperature for a few minutes or microwave it in a microwave-safe jar for no more than 15 to 30 seconds.