Bring two cups water to a boil. Add the bulgur and salt to taste, then simmer 20 minutes or so until the water is absorbed. Uncover, place a dishtowel over the pot, and cover again. Let the bulgur sit about 10 minutes (this helps it to become fluffy).
While the bulgur is cooking, make the dressing. Mix about 2 Tbsp. Dijon mustard with about a 1/4 cup red wine vinegar. Add the juice of half the lemon, then about 1/2 cup of the extra-virgin olive oil and a large pinch of salt. Whisk with a fork to combine.
When the bulgur is ready, toss it in a bowl with the dressing, arugula and dried cranberries. Add more lemon juice, salt, vinegar or olive oil to taste. Serve; garnish individual servings with feta and avocado.