Tangzhong sweet bread dough and maybe put some filling inside the buns.
Melonpan (メロンパン meronpan?), also known as Melon pan, Melon buns or Melon bread, are sweet bakery products from Japan, but also popular in Taiwan and China. They are made from enriched dough covered in a thin layer of crisp cookie dough. Their appearance resembles a melon, such as a rock melon (cantaloupe). They are not traditionally melon flavored,  but in recent times it has become popular for manufacturers to add melon to melon bread. Variations exist, including some with a few chocolate chips between the cookie layer and the enriched dough layer, and non-melon versions flavored with caramel, maple syrup, chocolate, or other flavors, sometimes with syrup, whipped or flavored cream, or custard as a filling. In the case of such variations, the name may drop the word "melon" ("maple pan") or may keep it despite the lack of melon flavor ("chocolate melon pan")
This recipe is adapted from MyFoodGeek
200 gram bread flour
7 gram dry yeast
2 tbsp sugar
½ cup warm water (about 100F)
1/2 teaspoon salt
From My Kitchen Snippets
120 gram flour
1/2 tsp baking powder
40 gram butter
50 gram sugar
extra sugar for dusting the tops
A few drop yellow food coloring –optional
2. Remove the dough from the mixer and place it in a lightly oiled container and cover with plastic wrap. Let is rise for an hour at warm place or until double in size.
3. While the dough is rising, make the cookie crust. Place the butter and sugar in the mixer fitted with the paddle attachment. Mix at high speed, scraping down the sides, until the butter and sugar are fully combined and turn to a pale yellow color.
4. Incorporate the egg and yellow coloring (if use) at low speed. Add the flour and the baking powder and mix until just combined. Remove from the bowl, shape into a log, wrap tightly in plastic, and refrigerate until firm.
5. Punch down the dough to remove the air. Remove the bread dough from the bowl and cut into nine equal pieces. Roll each dough piece into a tight ball and set aside.
6. Remove cookie crust from refrigerator and cut into nine equal pieces. Roll each piece of cookie dough into circle. Refrigerate the round disc again to firm them up slightly. Re-shape the bread dough again and cover the top with a piece of the cookie dough. Tuck the ends underneath. Roll the cookie dough surface over the sugar.
7. With a butter knife, make shallow incisions to obtain a criss-cross diamond motif on the top. Set it aside to rise for an hour or double in size.
8. Bake in a pre-heated 350 degree F oven for 20 minutes or until lightly brown on the surface. Cool on wire racks.