- Whisk together oil, vinegar, dill, shallot, mustard, and salt. Set aside.
- Fill four 500-mL (2-cup) Mason jars or 4 tall, narrow re-sealable food containers by layering ingredients into jars in the following order from bottom to top: vinaigrette, lentils, carrot, feta, and spinach. Screw on the lids. Shake well before serving.
Dried French green lentils (Du Puy lentils) are a great substitution for this salad as they hold their shape well when cooking. To cook, rinse well and add to boiling water. Reduce heat to medium-low and simmer 25 to 40 minutes, until tender but not mushy. Yield: 250 mL (1 cup) dried lentils produces about 500 mL (2 cups) cooked lentils.
You can prepare this salad ahead of time since it can be stored in the fridge for up to 24 hours.