First, prep lentils by placing 1/2 cup lentils and 2 cups of water in a medium-size pot. Bring to a boil and then reduce heat to low and let simmer for an additional 15 minutes. Remove from heat and drain remaining water and place in a tupperware and into the fridge to cool.
Next, prep veggies by dicing red onion, quartering cherry tomatoes, dicing cucumber, and slicing olives.
Once the lentils have cooled, mix all ingredients together and set aside.
For the Chicken
Preheat oven to 375ºF and rub a baking sheet with olive oil.
Next, place chicken breast on baking sheet and generously season each side with spices. Bake at 375ºF for 25-30 minutes depending on how thick the chicken breasts are. Place in a tupperware container and into the fridge to cool. once cooled, slice into bite-size pieces.
For the Dressing
Place all ingredients in a small bowl and whisk with a fork until combined.
For the Mason Jar Salad
Create your mason jar salad by placing 1/4 of the dressing at the bottom of each of the 4 jars. Then, place 1/4 of the diced chicken on top of the dressing. Add in a handful of spinach to each jar. Finish by adding the lentil mixture.