1) Cook lentils in boiling water with pinch of salt until tender, about 20 minutes. Drain.
2) Whisk dill mustard, juice of the lemons (about 1/2 cup of juice), salt and pepper in a large bowl.
3) Gradually whisk in oil to make the dressing.
4) Add diced bell pepper, diced onion, diced cucumber and lentils to the bowl and mix.
5) Drain salmon and add. Toss just to coat.
* This can be made vegetarian by omitting the salmon