Arrange one rack in the lower third of your oven and one in the upper third and preheat the oven to 450 degrees F. Line a rimmed baking sheet with parchment paper and place the sheet pan on the lower rack while it preheats.

Place the broccoli in a large mixing bowl and top with the oil, sugar, salt, black pepper, and red pepper flakes. Toss to combine.

Once the oven is preheated, carefully remove the hot baking sheet from the oven. Add the broccoli and spread it into an even layer with the flat sides of the florets touching the pan.

Return the pan to the lower third rack and bake until the broccoli is tender and beginning to brown at the tips and edges, about 16 to 18 minutes.

For extra crispiness, switch the oven to broil and move the pan to the upper rack. Bake for an additional 1 to 2 minutes until the broccoli becomes more caramelized.

Remove from the oven and squeeze the lemon over the top. Serve hot.