Cook the lentils: rinse in a sieve, add to a medium pot, pour in the broth and cover. Bring to a boil over medium heat, then reduce the heat to a minimum and cook for 15 minutes until lentils are soft. Drain the lentils, and while still hot, mash them thoroughly with a fork. I like to overcook the lentils – I add additional 2-3 tablespoons water at the beginning and cook the lentils about 4 minutes longer. This way the filling will be more smooth and creamy. If you don’t want to overcook the lentils it‘s good to puree the filling at the end so that the lentils are not noticeable.
Dice the onion, chop the sun-dried tomatoes finely and the garlic very finely.
Heat the oil in a frying pan (if you want to make vegetarian pierogi it‘s better to use clarified butter / ghee), add the onion and spices (paprika powder, cayenne pepper, thyme, cumin, and turmeric), cook over low heat for about 10 minutes. Add the garlic and cook for one minute more.
Combine the cooked lentils with sauteed onion and sun-dried tomatoes. Season with salt and pepper, add 2-3 tablespoons of oil from the sun-dried tomatoes jar so that the filling is not dry (you can swap a part of the oil with water).
Thinly roll out the dough, cut out rounds, scoop the filling with a teaspoon and place on the rounds, press the edges to seal.
Cook the pierogi in batches in a large amount of salted water. Once the pierogi float to the surface of the water, cook them for 2 minutes. Remove from the water with a slotted spoon.
They taste best pan-fried in oil / butter / ghee.