1 tbsp olive oil
Kosher salt, freshly ground pepper
1 garlic clove
1/2 c (packed) fresh basil leaves
1/4 c finely grated Parmesan
1/2 c extra-virgin olive oil
Preheat oven to 400°. Trim carrot tops, leaving some stem attached. Measure out 2 cups carrot tops and set aside; reserve any remaining carrot tops for another use.
Toss carrots with olive oil, then season with salt & pepper. Spread carrots out onto a rimmed baking sheet. Roast, stirring occasionally, until carrots are golden brown and tender, 25–35 minutes. Let cool.
While carrots roast, start pesto. In a food processor, pulse garlic and nuts until a coarse paste forms. Add basil, Parmesan, and reserved carrot tops; process until a coarse paste forms. Slowly add olive oil and pulse until combined and smooth. Season with salt and pepper. Spoon pesto generously atop roasted carrots.
MAKE AHEAD: Pesto can be made 1 day in advance. Press plastic wrap directly onto surface; chill. Carrots can be roasted 4 hours ahead. Let stand at room temperature.