Cut cantaloupe, remove seeds, cut away rind and slice into thin slices. Dice onion, and thinly slice tomatoes. Layer in a salad bowl. Combine dressing ingredients; lemon juice, cider vinegar, parsley, basil, salt, pepper, mustard, and mint in a container that you can seal and shake. Add the olive oil and vigorously shake until well combined. Pour over cantaloupe mixture, refrigerate for one hour. Top with crumbled Feta, serve.