Cap off the neutral wire
Despite being neutral, it can have lethal or fire-starting currents on it. (not least if your utility's drop wire has a problem). That's why neutral wires have insulation.
Your situation is not uncommon; range tops have no need for the neutral wire. Generally ovens and ranges are entirely 240V beasts. The only reason they ever wanted neutral is to have 120V available, to allow you to use a cheap, common incandescent light for the oven light, and sometimes for a 120V clock or electronics, and sometimes for a convenience receptacle on the oven. (old incandescents inside a 500 degree oven are as happy as Br'er Rabbit in the briar patch). Obviously, cooktops don't have oven lights, electronics have evolved to where they work fine on 240V, and UL won't let them fit convenience receptacles anymore.