In a medium bowl, combine the ketchup, vinegar, maple syrup, sea salt, and onion. Let sit for 15-20 minutes while the flavors mesh. This step also allows the dried onion to rehydrate.
Add the olive oil and stir to incorporate. Pour into a glass jar. Store in the refrigerator.
Recipe by Natural Living Family with Dr. Z & Mama Z at https://naturallivingfamily.com/homemade-french-dressing-recipe/