Cut tops off peppers or tomatoes; save.
Scoop out centers.
Dissolve 1 cup salt in 4 quarts cold water; pour over vegetable shells and tops; let stand 24 hours in a cool place.
Drain; rinse and drain thoroughly.
Combine cabbage, mustard seed, salt and pepper; press into shells.
Replace tops and fasten with toothpicks or sew with coarse thread.
Pack into hot jars, leaving 1/4-inch head space.
Combine vinegar, water and sugar.
Bring to a boil.
Pour hot liquid over peppers or tomatoes, leaving 1/4-inch head space.
Remove air bubbles.
Process 15 minutes in boiling water bath.