Yield: About 1½ cups 

Heat oven to 400°. Toss the tomatoes with ¼ cup oil and a big pinch of salt and roast until the skins burst and the liquid evaporates (about 20 to 35 minutes). Remove from the oven and allow to cool.

In a food processor, mix the tomatoes, egg, remaining ½ teaspoon salt and vinegar together for 1 minute. Slowly drizzle in the remaining oil until a thick mayonnaise forms.

Taste, adjust seasoning and acidity as desired, and serve.

Mayonnaise will keep for up to 10 days in the refrigerator.