Line a large baking sheet with paper towels and set aside.
Heat the oil in a large heavy skillet and over medium-high. Fry the plantain slices in batches until golden brown, turning halfway through (2-3 minutes per side). Transfer the fried plantains to the prepared sheet and set aside.
Add all sofrito ingredients to a food processor and blend to a course paste.
For the picadillo, heat the oil in a large heavy skillet over medium, add the sofrito and cook, stirring often, until it thickens, about 5 minutes. Add the ground beef and cook, stirring occasionally until the beef is cooked (no trace of pink), about 6 minutes. Stir in cumin, coriander, and oregano and continue cooking for 1-2 minutes, until aromatic.
Add the chopped tomatoes and tomato paste and cook, stirring occasionally, until the liquid has reduced (about 10 minutes), adding a splash of broth or water if needed. Stir in the olives, raisins, and capers, season to taste and turn off the heat.
Heat the oven to 375°F/190°C and lightly spray a 9-in x 13-in (or 9-in x 9-in) casserole dish with cooking spray.
Whisk the eggs, milk, and baking soda; season lightly, and set aside.
Layer the bottom of the casserole dish with half the fried plantain slices. Top with a layer of half of the picadillo mixture, gently smoothing it with a spatula to cover the plantains. Sprinkle half the cheese on top. Cover with a layer of the remaining plantains and top with the remaining picadillo. Pour the egg mixture evenly over the picadillo and sprinkle the remaining cheese on top.
Bake the pastelón for about 25 -30 minutes, or until set and the cheese is melted and golden.
Remove from the oven, let sit for 5 minutes, before cutting into squares and serving.