How to Make It
Cut 1 navel orange in half; squeeze juice from orange into a bowl to equal 2 tablespoons. Peel blood oranges and 1 remaining navel orange; cut crosswise into 1/4-inch-thick slices. Whisk together orange juice, oil, vinegar, syrup, salt, and pepper in a small bowl.
Cut radicchio heads in half lengthwise. Remove core from radicchio heads, and gently break into separate leaves. Tear fennel fronds to equal 3 tablespoons.
Arrange radicchio leaves, orange slices, and fennel slices on a large platter. Drizzle with dressing, and sprinkle with torn fronds.