Preheat oven to 450°F. Coat large baking sheet with cooking spray.

Cabbage:

Cut cabbage half into four wedges and cut out thick core, leaving the wedges as intact as possible.

Drizzle the cut sides with 1 T oil and sprinkle with 1/4 tsp each salt and pepper.

Place the wedges flat-side down on baking sheet.

Roast the cabbage for 12 min. Carefuly flip and roast until browned on both sides, about another 8 min.

Vinaigrette:

Combine mustard, vinegar, lemon juice, pepper and 1/4 tsp salt in a small bowl.

Add chives and oil, stir until well combined.

Transfer cabbage to serving plate and drizzle with vinaigrette while still hot. Serve hot or at room temperature.