Bring water to a boil for pasta. Salt water and boil pasta for 10 minutes or until "al dente." Meanwhile in the bottom of a mixing bowl combine about 1/3 cup extra virgin olive oil, rind and juice of a lemon, mustard to taste and season with salt and crushed red pepper.
Mince some garlic, halve or quarter cherry tomatoes and add to bottom of mixing bowl. Cut arugula into chiffonade ( not necessary with watercress). When pasta is done, drain it and return to pasta pot and toss with chiffonade of arugula; add dressing and toss until well combined.