Begin by preparing the dough: In a large kneading bowl, combine the lard, warm water, and salt, stirring gently to dissolve the salt and incorporate the lard. Add the all-purpose flour and dried oregano to the mixture, then knead thoroughly — either by hand for about five minutes or using your machine's kneading function — until the dough is smooth and elastic. Cover and let it rest for at least 30 minutes or, for best results, overnight in the fridge. This resting period allows the gluten to relax, yielding a tender pastry. Prepare the filling by blanching the tomatoes: immerse them in boiling water for about 30 seconds, then transfer to cold water to halt cooking. Peel off the skins and dice the tomatoes into cubes. Press the garlic through a garlic press and finely cube the red onions. Heat a splash of olive oil in a pan and gently sauté the garlic and onions until translucent and fragrant. Remove them from the pan, then increase the heat and sear the sirloin steak cubes until browned on all sides—this locks in the juices and flavor. Return the garlic and onions to the pan with the steak and add the diced tomatoes. Season with oregano, paprika, red pepper flakes, parsley, salt, and pepper. Allow the mixture to simmer for a few minutes, melding the flavors beautifully. Consider preparing this filling the night before and chilling it in the fridge; this resting enhances the depth of flavor. Boil the eggs until hard-cooked, then dice and fold them gently into the cooled meat mixture. Cut the rested dough in half and roll out one half on a floured surface until it's thin but sturdy. Using a 12-15 cm diameter cutter, cut out circles. Spoon 2-4 teaspoons of the filling onto each dough circle, avoiding overfilling to ensure easy sealing. Moisten the edges with a little water, fold the dough over into half-moons, and press the edges firmly with a fork to seal completely. Preheat your oven to 200 degrees Celsius. Arrange about eight empanadas on a baking sheet lined with parchment paper. Brush the tops with egg wash to achieve a beautiful golden crust. Bake for approximately 25 minutes or until they're golden and crisp. Serve warm, accompanied by drizzles of chimichurri sauce to add a fresh, herbaceous kick to the savory bites. Enjoy your homemade, comforting beef empanadas!