Finely chop your shallots and place them in a medium bowl. Pour in the red wine vinegar, ensuring the shallots are submerged. Allow this mixture to sit for 10–20 minutes.

After the shallots have pickled, remove them from the vinegar and set aside. In the same bowl, add the olive oil along with a pinch of salt and pepper to taste. Whisk the mixture vigorously for about 30 seconds until well combined.

In a large mixing bowl, combine the fresh spring mix, sliced radishes, sunflower seeds, and crumbled feta cheese. Gently toss together.

Just before serving, pour the tangy shallot vinaigrette over your salad mixture and toss gently to coat all ingredients evenly.