In a medium bowl, whisk together the vinaigrette ingredients until combined.
Add the shaved beets into the bowl, and toss to coat thoroughly. Let the beets marinate (at least 10-15 minutes) while you prepare the rest of the salad. I like to do this first, then handle slicing all the citrus.
On a large serving plate, arrange the citrus slices interspersed with the radicchio leaves—tear the leaves in half if they're too big.
Once the beets have marinated at least 10-15 minutes, pour the liquid off into a small jar—this is now our dressing.
Layer the beets into the salad, and drizzle the dressing over everything. Add a drizzle of olive oil.
To finish, sprinkle with toasted sunflower seeds, flaky sea salt, and freshly cracked pepper.
Serve immediately—though the salad also keeps very well and is delicious the next day. Just keep in an airtight container in the fridge.