Ingredients list is missing key ingredients

If you're eager to make this, don't bother waiting for the author's reply.

Just put enough cheese and tomato to fill up the bread slices. Since the jalapenos provide heat, add as much or little as suits your appetite for spiceness. There is no right or wrong amount other than your own preference.

You're right. When that happens, we're dependent on recipe author seeing & fixing, or someone who knows the recipe filling in.
Pending that, here is a load of similar recipes from an easy web search.
There are also ones using jalapeno poppers, if you want to search for them.
https://www.google.com/search?q=jalapeno+grilled+cheese+recipe+-popper&sxsrf=AOaemvICK4tzeBOtIgM3RNn6HR0wBgzOog%3A1642433879120&ei=V43lYfriBsGkqtsP1vq4kAw&ved=0ahUKEwi66rn_jrn1AhVBkmoFHVY9DsIQ4dUDCA4&uact=5&oq=jalapeno+grilled+cheese+recipe+-popper&gs_lcp=Cgdnd3Mtd2l6EAM6BwgAEEcQsAM6BggAEBYQHkoECEEYAEoECEYYAFDiBViqHmCrH2gCcAJ4AIABdIgB7AaSAQM2LjOYAQCgAQHIAQjAAQE&sclient=gws-wiz