Remove the husks of the tomatillos and, keeping them whole and unpeeled, wash well. Place the tomatillos in a large saucepan and cover with water. Boil for 5 to 10 minutes, until tender. Add 2 tablespoons of lemon juice to the jars and fill loosely with the tomatillos to 1/2 inch of the rim. Pour the cooking liquid to cover the tomatillos and remove any air bubbles. Seal the jars and process in a canner for about 40 minutes.
Another option is to can the tomatillos as an ingredient in a green salsa or relish. To make a tomatillo green salsa, combine 5 cups chopped tomatillos, 1 1/2 cups seeded and chopped long green chillies, 4 cups onions, 1 cup lemon or lime juice and 6 finely chopped garlic cloves; season with 1 tablespoon cumin, 3 tablespoons dried oregano, 1 tablespoon salt and 1 teaspoon black pepper. Heat the ingredients in a large saucepan over high heat, stirring frequently. Once the mixture begins to boil, reduce to a simmer for 20 minutes. Ladle into jars, leaving 1/2 of space to the rim and process in a boiling water canner for 15 to 25 minutes.
For your safety, wear plastic gloves while handling the hot peppers and avoid contact with eyes.
It is extremely important to follow the recipe amounts and instructions exactly as provided; any deviations in these amounts could alter acidity of the salsa and make it unsafe to consume.