In a food processor bowl fitted with a metal blade, place the egg yolk, lemon juice, white wine vinegar, and sea salt. Turn the food processor on and blend well.
Combine the oils in a glass measuring cup.
While the food processor is running, add the oils in a very thin stream until an emulsion is formed and the mixture thickens.
Scrape down the sides of the bowl and mix this liquid in.
Spoon the mayonnaise into a glass jar. Store, covered, in the fridge for about 5 days.
Notes
Store in the refrigerator covered for up to 2 weeks. Nutritional value is based on 1 cup.