In a large skillet with high sides or in a large saucepan, toast the pumpkin seeds, cumin seeds, and oregano over high heat. Toss to make sure they don't burn, but toast until fragrant, about 3 to 4 minutes. Remove from the heat and transfer to a blender or spice grinder and process until ground. Set aside.
In the same skillet, heat the oil over medium-high heat. Add the onion, tomatillos, garlic, and jalapeños and cook until slightly browned, 4 to 5 minutes, tossing a couple of times, but not stirring too much. Carefully place the vegetables in a blender or food processor. Then add the broth, cilantro, parsley and salt and process until puréed. Pour back into the skillet and add the ground pumpkin seed mixture. Let simmer until flavors are well combined, about 15 minutes, stirring occasionally. Serve over fresh tilapia or another white fish with fresh lime wedges