Cumin Scented Potatoes

1 1/2 pounds russet or Yukon Gold potatoes, peeled, cut into 1/2-inch cubes, and submerged in a bowl of cold water to prevent browning
2 tablespoons canola oil
1 tablespoon cumin seeds
1 small red onion, cut in half lengthwise and then into 1/2-inch cubes
1 teaspoon ground turmeric
2 teaspoons coarse kosher or sea salt
1 teaspoon cayenne (ground red pepper)
1 medium-size tomato, cored and cut into 1-inch cubes
2 tablespoons finely chopped fresh cilantro leaves and tender stems

Drain the potatoes and pat them dry.
Heat the oil in a medium-size saucepan over medium-high heat. Add the cumin seeds and cook until they sizzle, turn reddish brown, and are fragrant, 5 to 10 seconds. Add the potatoes, onion, and turmeric, and stir-fry until the potatoes and onion are lightly browned around the edges, 4 to 6 minutes.
Sprinkle in the salt and cayenne, and stir once or twice. Pour in 1 cup water and bring to a boil. Reduce the heat to medium-low, cover the pan, and cook, stirring occasionally, until the potatoes are almost fall-apart tender, 18 to 20 minutes.
Stir in the tomato and cilantro, and cover the pan. Simmer, stirring occasionally, until the tomato is warmed through, about 2 minutes. Then serve.