homemade mayo is one of the easiest things to make if you have a hand blender and wayyyyyy tastier, addictingly so actually
you need some real, strong dijon mustard though, like the kind trader joe's sells for ~$3
in a tall glass or container:
1 raw egg
1 soup spoon dijon
1 soup spoon apple cider vinegar
salt/pepper
a bunch of vegetable oil (about 1.5 cups? eyeball - watch some youtube videos)
blend
don't overblend once it seizes or it can de-emulsify