Combine sweet and jalapeno peppers, vinegar, water and salt in blender. Whirl until finely chopped, about 1 minute.
Boil sugar and pepper mixture in large pot 4 minutes. Remove from heat. Cover; let stand for 20 minutes.
Boil another 4 minutes. Add lemon juice; boil 2 minutes. Add pectin. Boil 1 minute, stirring.
Remove from heat. Pour into canning jars, sterilized according to manufacturers instructions; leave 1/4-inch of headspace at top of each; seal jars. Store jars in refrigerator up to 6 months. Makes about 6 cups. (Nutrition facts are for 1 tablespoon.)
If you prefer a thinner jelly, cook it for a slightly shorter time. Also, wear rubber gloves when working with hot peppers.