Blend cider vinegar, catsup, white sugar, pimentos, green bell pepper, lemon juice, onion, mustard, and salt in a blender until smooth. Stream olive oil into the vinegar mixture while blending; blend until the dressing emulsifies.
Pour dressing into a bowl, cover with plastic wrap, and refrigerate until chilled, at least 30 minutes.
All done! Now take a photo, rate it, and share your accomplishments!