INGREDIENTS
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2 tbsp. chopped fresh flat-leaf parsley
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1 1/2 tbsp. chopped fresh rosemary
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1 large garlic clove, chopped
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2 tsp. Dijon mustard
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3 tbsp. extra-virgin olive oil, divided
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Kosher salt
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Freshly ground black pepper
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1 lemon, cut into thin slices, divided
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4 small bone-in, skin-on chicken breasts (about 2 1/2 lbs. total)
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2 bunches Broccolini (about 1 lb.)
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1 red onion, cut into 1/2" wedges
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1/2 tsp. crushed red pepper, plus more for serving