My sis found this marble butter cupcake recipe by Kimiya Lim and told me to give it a try. The steps seem simple enough to follow so gave it a try.
Don't know why my bakes always rose and crack in the oven then sink after cool. Posted on the Facebook group "Home-cooked Delights 家常便饭" page to ask for advice and some members told me to try to lower the temperature and bake longer as well as to only fill 2/3 of the baking cup.
Shall give this recipe another try with the suggestions given.