Separate the lettuce leaves; rinse and wipe them dry with a clean tea towel. Chill in the refrigerator to keep them fresh and crispy.
Make the dressing: mix the lemon zest &juice with the mustard that was given with the gravadlax. Add a spoonful of olive oil, or until you get a thick dressing. Taste it, and adjust the seasoning to your liking - it might need a pinch of sugar or salt& pepper. Set aside.
Blanch the peas for 2 minutes in boiling water or steam above boiling water. Rinse under cold water, drain and set aside.
Slice the beetroot into thin wedges. Set aside.
Slice the zucchini with a potato peeler into long ribbons. Brush the strips with oil then griddle or barbecue them in batches on each side for a minute or two until lightly charred. When finished, toss them with the peas and half of the dressing.
Arrange the lettuce leaves on a serving dish. Add the vegetables. Slice the salmon and scatter on top of the salad. Drizzle with the dressing and serve.