This simple homemade mayo recipe calls for:
1 egg yolk
2 teaspoons lemon juice
1 1/2 teaspoons mustard
1 teaspoon sugar
1 cup of olive oil
Simply blend all ingredients except oil in a blender just until mixed together, and then slowly add the oil until the mixture starts to thicken a little, maybe a minute or so. Refrigerate up to 1 week.
Feel free to experiment with different oils!