1. Prepare pasta according to package directions.
2. While pasta is cooking, whisk together the
mustard, honey, buttermilk, mayonnaise and celery
seed in a large bowl. Set aside.
3. Grill or broil tuna until firm (cooked).
4. Transfer tuna to a cutting board and let cool for
a few minutes.
5. Toss together the pasta, mustard sauce, cucumber
and red bell.
6. Dice the tuna and add to pasta mixture.
7. Toss gently and serve.