Start by gathering all your ingredients and letting the egg yolks sit at room temperature for about 30 minutes.
In your mixing bowl, add the two egg yolks and Dijon mustard. Whisk them together until smooth and the color lightens a bit.
Slowly drizzle in the high-oleic sunflower oil while whisking continuously. This gradual addition is crucial for creating a stable emulsion.
Once thickened, mix in the sea salt and lemon juice. Taste and adjust seasoning as desired.
Transfer the mayonnaise to a clean jar with a tight-fitting lid and store in the refrigerator.
