Step 1

Whisk together the vinegar, zest, lemon juice, mustard, salt, and pepper in a medium mixing bowl. Gradually add the olive oil, whisking constantly. Add the broccoli and toss to coat. Cover and refrigerate for 1 hour.

Step 2

Stir in the tomatoes, hazelnuts, and basil. Cover and allow to sit at room temperature or in the refrigerator for another 15 minutes before serving.