Preparation

Preheat grill with HexClad BBQ Grill Pan placed on the center of the grill over medium-high heat, 15 minutes. 

In a large bowl, toss the broccoli with 2 tablespoons of the oil. Add broccoli to the grill pan (reserve the bowl) and the cut lemon cut side down on the grill to the side of the basket. Grill (covered if using a gas grill), turning occasionally, until crisp tender and lightly charred, about 10 minutes for the broccoli and about 3 minutes for the lemon.

Transfer grilled broccoli back to the reserved bowl. Squeeze juice from lemon halves, removing any seeds (about 2 tablespoons juice) and toss broccoli with squeezed lemon juice and remaining 2 tablespoons of the oil.

Finely zest remaining lemon (about 1 teaspoon zest) with a microplane or the small holes of a box grater and toss zest in a medium bowl with parmesan, pistachios, parsley, and red pepper flakes. Cut remaining zested lemon into wedges. Sprinkle parmesan mixture over grilled broccoli and serve with lemon wedges.