Preheat the oven to 180ºC. Halve the capsicums lengthways, carefully cutting through the stalk. Remove the pith and seeds. Cook the capsicum shells in boiling water for 6–8 minutes or until tender. Drain thoroughly and place on paper towel.
Cook the linguine in boiling water for 10 minutes, or according to the packet instructions, until al dente. Drain well.
Beat the eggs with the cheese, mustard powder, milk, chives and marjoram. Stir in the tomatoes and seasoning to taste.
Place the capsicums in an ovenproof dish or roasting tin, supporting them with pieces of crumpled foil, if necessary, to ensure that they are level (otherwise the filling will spill out). Half fill each capsicum with linguine, then spoon the egg and cheese mixture over the pasta.
Bake for 20–25 minutes or until the filling is set and beginning to turn golden. Serve garnished with whole chives, with an accompaniment of mixed salad leaves, if you like.