Hard-boil an egg over medium-high heat (about 10 minutes), then cool it in ice water. Peel and chop the egg. Wash the tomatoes, finely dice them removing seeds and stems. Drain and chop the tuna. Mix the egg, tomatoes, tuna, and coriander greens together. Season with salt and pepper.
For the cheese filling, mash the cheese. Mix with an egg and fresh herbs. Wash the onions and cut into fine rings, then mix in. Season with chili powder.
Preheat the oven to 200 °C (392 °F). Line baking trays with parchment paper.
Cut the dough sheets into 6 strips, each roughly 10 cm wide. Melt the butter over low heat and brush some onto the strips, reserving the remaining butter. Place 1 tablespoon of filling on the bottom of each strip and roll up tightly. Brush the rolled parcels with the remaining butter.
Place the dumplings on the prepared trays and bake at 200 °C (392 °F) until golden brown, 20-25 minutes, turning once halfway through.