Cut each okra pod in half lengthwise and set aside. If there are any pods longer than 4 inches, cut them in half crosswise and then lengthwise.
Heat the olive oil in a 4-quart saucepan over medium heat until shimmering. Add the onions along with the salt and cook until they begin to turn golden, approximately 4 minutes. Add the garlic and cook for 1 minute longer. Add the tomatoes and bring the mixture to a boil. Decrease the heat to low and add the ginger, pepper, cardamom and okra. Stir to combine. Cook, uncovered for 20 minutes. Remove from the heat, taste and adjust the seasoning as desired. Serve immediately.