Chef Floyd Cardoz shares his spin on the classic party appetizer.
Heat a large skillet over medium heat. Add 2 tablespoons oil and nigella seeds and cook for 1 minute. Remove from skillet and set aside.
Add remaining 1/4 cup plus 2 tablespoons oil to skillet and add onion and shallots. Add sugar and season with salt and pepper and cook, stirring, until caramelized, about 15 minutes. Remove from heat and let cool.
Transfer caramelized onion mixture to the jar of a blender and add yogurt, sour cream, grainy mustard, lime juice, dry mustard, and cayenne pepper. Season with salt and pepper and blend until smooth. Fold in reserved nigella seeds and serve.