Heat the vegetable oil in a pan over medium heat.
Add the finely chopped onion and minced garlic. Sauté until the onion is translucent.
Add the ground turmeric, cumin, coriander, red chili powder, and salt. Stir and cook for a couple of minutes until fragrant.
Add the flaked tuna to the pan. Stir to combine and cook for about 5 minutes.
Remove from heat and add lemon or lime juice. Mix well. Optionally, you can stir in some chopped fresh coriander. Set aside to cool.
In a large bowl, combine the flour, baking powder, and salt.
Add the vegetable oil and mix well.
Gradually add water, a little at a time, until the dough comes together and is smooth and elastic.
Knead the dough on a floured surface for a few minutes. Cover and let it rest for about 30 minutes.
Preheat the oven to 375°F (190°C).
Divide the dough into small balls (about the size of a golf ball).
Roll out each ball into a thin circle on a floured surface.
Place a spoonful of the filling in the center of each circle.
Fold the dough over the filling to form a half-moon shape. Seal the edges by pressing them together with your fingers or a fork.
Place the filled dough on a baking sheet lined with parchment paper.
Bake for about 20-25 minutes, or until the Gulha are golden brown and crisp.
Enjoy your meal!