Preheat oven to 425 degrees F. Line two baking sheets with foil and spread out bread cubes evenly amongst pans. Drizzle ½ T olive oil over each pan of bread and season with salt and pepper. Toss to combine. Bake for 12-15 minutes, tossing once halfway through.
Wrap the beets in aluminum foil and roast in the oven alongside the bread, for about 10 minutes. Remove from oven, and allow to cool slightly; then thinly slice.
Combine sliced beets, cubed watermelon, sliced red onion, arugula, mint, basil, and cheese in a large bowl.
Whisk lemon dressing ingredients together until well-combined.
Once bread cubes are finished toasting, remove from oven and let sit for 5 minutes before adding them to salad. Pour dressing over salad and toss to combine. Serve immediately.
Note: if not serving immediately (such as for a picnic), save step 5b until ready to serve. Add the toasted bread cubes and dressing at the last minute to prevent the bread from getting soggy.
Recipe adapted from: http://dishingouthealth.com