First, toast the hazelnuts. Preheat the oven to 350°F. Spread the hazelnuts in an even layer on a small baking sheet. Toast for 8-10 minutes, shaking the pan halfway through, until fragrant and lightly golden. Remove from the oven, let cool slightly and set aside.
Now, make the vinaigrette. In a small bowl or jar, whisk together the olive oil, orange zest and juice, lemon zest and juice, maple syrup, Dijon mustard, garlic, salt, and pepper until smooth and emulsified. Taste and adjust seasoning as needed.
In a large serving bowl, add the radicchio and endive.
Layer the grapefruit rounds and orange segments over the greens. Sprinkle with the toasted hazelnuts, pistachios, Parmesan, mint, and pomegranate seeds. Drizzle with vinaigrette to coat and toss gently.
Season with salt and pepper, and serve immediately!