Add potatoes and cook until tender but still firm, about 10 minutes.
Drain and set aside.
Place eggs in a saucepan and cover with cold water. Bring water to a boil and immediately remove from heat. Cover and let eggs stand in hot water for 10 to 12 minutes.
Remove from hot water, cool, peel and chop.
In a large bowl, whisk together the mayonnaise, mustard, turmeric and onion.
Add the still-warm potatoes and stir until evenly coated. Gently mix in the hard-cooked eggs.