In a small mixing bowl, whisk together the lemon juice, red wine vinegar, minced garlic, and Dijon mustard until combined. Allow it to sit as you assemble the other ingredients.

While continuously whisking, slowly drizzle in the olive oil until the vinaigrette thickens and becomes emulsified. Season with salt and pepper to taste.

Slice the radishes thinly using a sharp knife and slice the red onion into thin rings. Place the sliced vegetables into a large mixing bowl.

Chop the fresh dill finely and add it to the bowl with the radishes and red onion.

Pour the prepared vinaigrette over the vegetable mixture and gently stir to coat them completely.

Crumble the feta cheese over the salad and carefully fold it in, ensuring the cheese incorporates without breaking down too much.

Transfer the salad to a serving bowl and serve immediately for the best crunch and freshness.