How to Make It
Preheat oven to 425°F. Combine onion, bell peppers, and oil on a baking sheet. Bake at 425°F until tender and lightly charred, about 15 minutes.
Place potatoes in a large saucepan with water to cover by 2 inches; bring to a boil over high. Reduce heat to medium-low; simmer until potatoes are barely tender, about 5 minutes. Add eggs to pan. Cook until potatoes are tender, about 12 minutes. Remove eggs and place in a bowl filled with ice water; let stand 5 minutes. Drain potatoes; cool 5 minutes.
Combine mayonnaise, yogurt, mustard, juice, parsley, dill, salt, and pepper in a medium bowl. Peel cooked eggs and chop. Add eggs, potatoes, and onion mixture to mayonnaise mixture; stir gently to combine. Serve immediately, or chill before serving.