Rinse the lentils under cold water until the water runs clear.

Put lentils in a medium pot with 4 cups of water. Bring to a boil, then lower heat to a simmer. Cook until tender but not falling apart, about 20–25 minutes. Drain any excess water if needed.

While the lentils simmer, rinse the rice under cold water until it runs clear.

Add the rice to the pot with the lentils. If needed, add up to 1/2 cup more water so the rice has the proper rice-to-water ratio. Season with 1 tsp salt and the optional spices. Cover and cook on low until the rice is tender, about 15–20 minutes.

Meanwhile, heat 3 tablespoons olive oil in a large skillet over medium heat.

Add the sliced onions and a pinch of salt. Cook slowly, stirring occasionally, until the onions are deeply golden and caramelized — about 20–30 minutes.

Lower the heat if they begin to brown too fast.

When rice and lentils are done, fluff gently with a fork and adjust seasoning.

Transfer to a serving bowl and spoon the caramelized onions over the top. Serve warm.