The commercially produced stick pepperoni is a cooked dry sausage. I believe it is cooked to about 120F internal temp, this would require cooking at relatively low temp like 140-145F and high humidity to help heat transfer.
Not possible to do this in an ordinary oven as the lowest temp is usually 170F. We once tried to zap the sausage for about 20 Min @170F and letting it hang in there for about another 30 min to carry over and it produced a texture somewhat similar to commercial pepp. but not exactly the same.