How do you say "fire lotus" in japanese?

some general knowledge on Japanese helps:

the majority of kanji (=chinese characters) can be read either "sort of Chinese" (= called onyomi, as Japanese has taken over a lot of Chinese words over a span of a fe centuries, just as we've taken over a lot of Latin/Greek vocab)

or Japanese, called "kunyomi"

for the kanji 火 that is ka (chin.) or hi (jap.), both meaning fire, of course

for the kanji 蓮 that is ren (chin.) or hasu (jap.), both meaning lotus, of course.

Words that are made up out of baked together kanji, are in their majority pronounced in "onyomi", and as a rule: in BOTH components of a compound.

So, your made up compound "fire lotus" = 火蓮 would be read as "ka-ren" by Japanese

Japanese Word For Lotus