Warm German Potato Salad

Ingredients

• 2 pounds starchy potatoes
• 2 tablespoons olive oil
• 1/2 small finely chopped red onion
• 1/2 teaspoon sugar
• 1/4 teaspoon pepper
• 2 tablespoons mustard
• 1 small thinly sliced cucumber
• 1/2 teaspoon salt
• 1/4 cup white vinegar