In a large pot, place cucumbers, cauliflower, onions and enough boiling water to totally cover the vegetables.
Pour ½ cup salt over vegetables and let stand about ½ hour; drain.
Add red pepper.
In another large pot, combine 3 cups vinegar and 2 cups sugar.
Bring to a boil and add vegetables.
In a separate bowl, make a paste using 1 cup flour, 1 cup sugar, 1 ½ tsp. dry mustard, 2 tsp. celery seed, 2 tsp. turmeric and 1 cup vinegar.
Add to vegetables and cook for an additional 5 minutes.
Fill canning jars while mix is still hot; add lids and turn upside down in a pan filled with enough hot water to cover the rings.
Allow to cool; remove jars from pan right side up.
Check to make sure all lids sealed.
If any have not sealed, store pickles in the refrigerator.