Yucatecan tamales filled with chaya and pumpkin seeds wrapped in banana leaves are a regional treasure. This vegetarian dish is a healthy, high protein meal with fresh, earthy flavors.
Toast the raw pumpkin seeds in a dry skillet over medium heat for 4–5 minutes, stirring constantly until they are fragrant and lightly golden, then cool and grind them finely.
Heat 1 tbsp olive oil in a skillet over medium heat; add chopped onion and sauté until soft, about 3–4 minutes. Add chopped chaya leaves (or Swiss chard) and cook until wilted, about 2 minutes. Stir in epazote if using, salt, and black pepper.
In a large bowl, combine masa harina, the remaining 1 tbsp olive oil, and 1 cup vegetable broth. Mix with hands, gradually adding more broth until a soft, spreadable dough forms.
Cut banana leaves into 12" squares; pass each leaf over an open flame for a few seconds to make them pliable. Spread about 1/3 cup masa onto each leaf, leaving a border.
Spoon the sautéed chaya filling and a generous sprinkle of ground pumpkin seeds onto the masa. Fold the leaves to enclose the filling, then tie securely.
Arrange tamales seam side down in a steamer basket over simmering water. Cover and steam for 60 minutes, checking the water halfway through and adding more as needed to prevent drying.