1 large egg, room temperature
1 tablespoon Dijon mustard
1 tablespoon red or white wine vinegar
1/4 teaspoon kosher salt
1 cup canola oil, divided
1 teaspoon fresh lemon juice
Small food processor or immersion blender (using too large of a food processor prevents mayonnaise from emulsifying)
Add egg, mustard, vinegar and salt to the bowl of a small food processor. Process for 20 seconds. Scrape the sides and bottom of bowl. Turn the processor on and slowly add 1/4 cup of the oil in tiny drops.
When the mixture begins to thicken and emulsify, add the rest of the oil in a thin stream. When all the oil has been added, scrape the bottom and sides of bowl and process for 10 seconds. Add lemon juice or extra vinegar to taste.
If mayonnaise seems too thin, turn on processor and slowly stream in more oil until mayonnaise thickens. Store covered in refrigerator for up to 3 weeks.