Have you tried low-fat trigger-free mayo or is it the eggy-ness of mayo in general that turns your tum?
And btw, in that case I'd go for the olive oil instead of butter sub. Measure it out in teaspoons so you don't use much, but you don't need to. Remember that as we don't have much fat in our diet we should try and make sure that as much of it as possible is good fats.