Melt the butter and brush onto the pieces of filo pastry, placing one on top of the other.
Use a round cutter to pull out round circles of the filo pastry and put in a muffin tin or a similar pan. The circles need to be a little bigger than bottom of the muffin tins to give the tartlets edges on top. Bake at 350F for 5-6 minutes until they have a hint of color. Let cool.
Chop the salmon with a knife and stir with sour cream, mayonnaise, dill and shallot. Season with salt, pepper and lemon zest. Put a small amount of the salmon salad into the tartlets. Top with grated Castello Extra Mature Cheddar and some dill.
If you have any leftovers the salmon salad is also great on a piece of bread.