Heat the oil in a medium-size saucepan over medium-high heat. Add the onion and cardamom pods, and stir-fry until the onion turns light brown around the edges, 3 to 5 minutes.
Stir in the blended yogurt and continue to cook, uncovered, stirring occasionally, until the watery liquid evaporates from the yogurt and leaves behind reddish-brown curd like pellets, 12 to 15 minutes.
Sprinkle in the turmeric and incorporate it into the tart sauce. Add 2 cups water and the beans, salt, garam masala, and cayenne. Bring the curry to a boil. Then lower the heat to medium and gently boil the sauce, uncovered, stirring occasionally, until it has thickened, 10 to 15 minutes.
When ready to serve, garnish.
with a bunch of chopped fresh cilantro, and serve with some plain or Jeera Rice!