Spread the butter on one side of the slices of toast.
Put the slices of toast in a frying pan, buttered side face down.
Heat the frying pan - carefully.
Add the Gruyere on both slices of toast & put a lid on the frying pan.
About 5 min later the Gruyere should be melted. Add the Spanish peppers, pile the slices & put the lid on for some more minutes (max 3 min!).
Transfer the slices of toast to a plate & cut into halves.
Enjoy at once w/ help of lettuce leaves.
Notes
Of you don’t happen to have any baked Spanish pepper, but only fresh peppers then you only need to bake the Spanish peppers on a tray lined w/ baking parchment at about 175° C w/ fan for about 20 min.