Bring 3 cups of water to a simmer in a medium pot. Once it’s simmering, add the lentils. Let the pot return to a simmer and place a lid tilted on top. Allow the lentils to simmer for about 20 minutes. After 20 minutes, taste the lentils to test the texture. They should be tender but not mushy. Drain the lentils in a colander and rinse with cold water to cool.

While the lentils are cooking, make the vinaigrette. Whisk the lemon juice, apple cider vinegar, Dijon, sugar, garlic powder, salt, and pepper in a small bowl until combined.

While constantly whisking, slowly pour the oil into the bowl until smooth. Set aside.

To make the salad, add the cooked lentils and spinach to a large bowl. Add the cranberries, diced apples, feta, and walnuts, then fold.

Drizzle the salad with the vinaigrette and toss to combine.