Red pepper relish and hot pepper relish can be found in many hot dog and burger joints, diners and markets al over New England, though perhaps less so than when I was a kid.
Typical pepper relishes in NE are made very much like Phil's recipe. They usually are made with red bell pepper or a combination of red bells and green bells (others can certainly be subbed; I use banana, like Phil, or yellow bell), contain onion, and are sweetened (usually substantially) with sugar. The hot relishes are usually made the same way but crushed red pepper is added at the beginning and simmered along with everything else. (I'm with Bryan. I don't use CRP for much as it is seedy and lacks chile flavor, though it has heat. For superior flavor plus heat, color and no seeds: Aleppo pepper from Penzey's.) Some cooks (like me) swirl oil into the mix for more body and, especially, to carry the fat soluble flavors and heat of the hot chile. Mustard seed is often included in NE-style relishes, as seen below:
New England-style Hot Pepper Relish
3 c finely chopped red bell pepper
1 c Finely chopped yellow bell, banana or green bell peppers (or a combination)
2 c finely chopped onion
2 c apple cider vinegar
.75 c sugar
1 T whole brown mustard seed
2 t salt
1 or 2 T crushed red pepper (or Aleppo, my pref)
3-4 T oil
In a heavy medium saucepan combine the pepper, onion, cider vinegar, sugar, mustard seed, salt and red pepper flakes or Aleppo. Bring mixture to a stong simmer over med-high heat then reduce to med heat and cook, stirring occasionally, for about 1 hour, or until reduced to about 3 cups. Stit in the oil, cook 10 mn more. Cool off heat, stirring occasionally, then pack for the fridge.
Wide open for variations, you can add different spices or aromatics, and you can certainly use different peppers (I sometimes cheat in small whole hot peppers like piri-piris or dundicuts to add more heat).
