How to Make It
In a large saucepan, cook the bacon over moderate heat, stirring often, until crisp, about 5 minutes. Drain the bacon on paper towels and set aside. Reserve 2 tablespoons of the bacon fat in the saucepan; discard the rest.
Add the onion to the bacon fat and cook over low heat, stirring occasionally, until softened, about 8 minutes. Add the ginger, curry powder, jalapeño and cinnamon and cook until fragrant, about 4 minutes. Stir in the lentils, water and stock and bring to a boil. Reduce the heat to low, cover and simmer until the lentils are tender and most of the liquid has been absorbed, about 35 minutes. Season with salt and pepper.
Meanwhile, in a medium bowl, sprinkle the cucumber slices with a large pinch of salt and let stand for 15 minutes. Drain and pat dry.
In a small skillet, toast the cumin and coriander over moderate heat until fragrant, about 40 seconds; transfer to a medium bowl and whisk in the buttermilk, sour cream and orange zest. Stir in the cucumber slices and season with salt and pepper.
Transfer the lentils to a large shallow bowl. With a rubber spatula, gently stir in the orange juice and season with salt and pepper. Spoon the cucumber salad over the lentils. Sprinkle the bacon and tomatoes over the cucumbers and serve warm or at room temperature.