Wash potatoes and cut into bite-size pieces.
Add potatoes to a large pot, then pour over enough water to cover potatoes by 1". Season potatoes generously with salt. Bring water to a boil over high heat, reduce heat to medium and cook at rapid simmer until potatoes are easily pierced with a knife, about 10 minutes. Drain potatoes.
While potatoes are hot, toss them with ⅛ cup of vinegar.
In a small bowl mix ¼ cup pesto, ⅓ cup mayonnaise, and the zest and juice from ½ lemon.
Drain any excess vinegar from potatoes.
Toss potatoes the bacon, green onions, and the pesto mixture until all ingredients are incorporated.
Transfer to a serving dish. Serve warm, room temperature, or cold.