Prep everything before you cook: dice the sweet potato into 1/2-inch cubes, finely dice 1/2 onion, mince 2 cloves garlic, and measure out spices and broth. Mise en place keeps the cooking flow smooth and prevents overcooking delicate ingredients like spinach.

Heat a medium Dutch oven or heavy saucepan over medium heat and add 2 tablespoons of olive oil. Warm oil to shimmering (not smoking) — this is the ideal fat temperature to sauté aromatics without burning them.

Add the diced onion and a pinch of salt; sauté for 4–5 minutes until softened and lightly golden. Salt draws moisture from the onion, helping it to soften and caramelize more quickly, building a sweet base flavor.

Stir in the minced garlic, 1 teaspoon ground cumin, and 1 teaspoon smoked paprika. Toast the spices in the oil for 30–45 seconds until fragrant—this blooms the spice oils and deepens the stew’s aroma. Be careful not to burn the garlic; stir constantly.

Add the diced sweet potato and cook, stirring occasionally, for 4–5 minutes so the edges pick up color. Browning the sweet potato adds caramelized flavor and helps it hold shape through simmering.

Pour in 1/2 cup diced tomatoes (with juices) and the 2 cups vegetable broth. Scrape any browned bits from the pot bottom—those are flavor gold. The broth-to-lentil ratio keeps the stew brothy but hearty; you can add more broth later if you prefer a thinner soup.

Bring the pot to a gentle boil, then reduce heat to maintain a simmer. Cover partially and simmer for 10–12 minutes, or until the sweet potato is just tender when pierced with a fork. Simmering allows flavors to meld and the sweet potato to soften without turning to mush.

Stir in 2 cups cooked lentils. Since these lentils are already cooked, we add them later to warm through without breaking down. Simmer uncovered for 4–6 minutes so the lentils absorb some broth and the stew thickens slightly.

Fold in the baby spinach handfuls (about 4 cups loosely packed). Spinach wilts quickly; stirring it in at the end preserves bright color, texture, and nutrition.

Taste and adjust seasoning with 3/4 teaspoon salt, 1/2 teaspoon black pepper, and, if desired, 1 teaspoon lemon juice to brighten the dish. Acid at the end wakes up the flavors and balances sweetness from the potato.

While the stew finishes, toast 2 slices whole-wheat bread until golden. Rub the warm toast with a very light brushing of olive oil or a crushed garlic clove for extra flavor. Toast serves as both vehicle and texture contrast to the stew’s soft components.

Serve the stew hot in bowls with a slice of toasted whole-wheat bread on the side or torn and dipped into the stew. Garnish with an extra drizzle of olive oil or a few red pepper flakes if you like heat.