Step 1

Cut both ends off the yellow onion and cut evenly into 2 halves. Remove and discard skin. Place onion halves on a cutting board with cut-sides down. Make vertical slices against the grain, then turn and slice across the cuts to chop. Chop again if you'd like smaller pieces. You should have about 2 cups chopped onion.

Step 2

Heat olive oil in a large skillet over high heat. Transfer onion and salt into the hot oil. Cook until onions are deep brown in color, 7 to 8 minutes. Add shallots and red onions; stir and saute until they start to soften and sweeten, 3 to 4 minutes. Turn off the heat and stir in garlic and dried onion. Set aside to cool completely, about 20 minutes.

Step 3

Combine mayonnaise, sour cream, pepper, cayenne, and cooled onion mixture; mix until thoroughly combined. Cover and chill in the refrigerator for 4 to 12 hours, or overnight.

Step 4

Remove dip from the refrigerator and stir in green onions and chives. Taste and adjust seasoning. Transfer dip into a serving bowl and garnish with more green onions and chives to serve.