Boulettes à l'oignon (Meatballs with Onion)

Ingredients

• 1 yellow onion, roughly chopped
• 1 medium russet potato
• 3 lbs ground beef
• 2 teaspoons salt
• 1 teaspoon white pepper
• 1 teaspoon nutmeg
• 1 ¼ teaspoon mace
• ¼ cup + 2 tablespoons matzo meal
• 2 tablespoons sunflower oil
• ¼ cup sunflower oil
• 2 yellow onions, halved and thinly sliced
• 1 teaspoon salt
• ¾ teaspoon white pepper
• 1 teaspoon turmeric