Prepare for Roasting: Preheat your oven to 425°F / 220°C. Lightly coat a large baking sheet or roasting pan with cooking spray.
Make the Marinade & Toss: In a mini food processor or a small bowl, blend the olive oil, minced garlic, red wine vinegar, Dijon mustard, salt, and pepper until smooth.
Place the quartered fennel in a large bowl, pour the marinade over it, add the grated Parmesan, and toss well to coat every piece.
Roast to Perfection: Arrange the coated fennel quarters in a single layer on the prepared baking sheet.
Roast for 35 to 40 minutes, or until the fennel is tender when pierced with a fork and the edges are beautifully golden brown and caramelized.
Don't overcrowd the pan!
Spreading the fennel in a single layer ensures it roasts to a perfect golden brown instead of steaming. Use two baking sheets if necessary.
When quartering the fennel, leave a small part of the core attached to each piece. This helps the layers stay together during roasting.
