Follow these steps carefully to achieve perfectly roasted beets and juicy, flavorful grilled chicken. The process is straightforward, with most of the time being hands-off while the beets roast and the chicken marinates.

Step 1: Prepare and Roast the Beets

1. Preheat Oven: Begin by preheating your oven to 400°F (200°C). Position a rack in the center of the oven for even cooking.
2. Wash and Prep Beets: Thoroughly scrub the beets under cold running water to remove any dirt. Pat them dry. There’s no need to peel them before roasting; the skins will slip off easily once cooked. Trim off the leafy tops and the root tail.
3. Cut the Beets: Cut the beets into uniform, 1-inch cubes. Consistency in size is key to ensuring they all cook at the same rate. Place the cubed beets in a medium-sized mixing bowl.
4. Season the Beets: Drizzle the beets with 2 tablespoons of olive oil and 1 tablespoon of balsamic vinegar. Sprinkle with 1/2 teaspoon of sea salt and 1/4 teaspoon of black pepper. Use your hands or a spatula to toss everything together until the beets are evenly coated in the glistening mixture.
5. Roast: Spread the seasoned beets in a single layer on a parchment-lined baking sheet. It’s important not to overcrowd the pan, as this will cause the beets to steam rather than roast. If necessary, use two baking sheets.
6. Cook to Perfection: Place the baking sheet in the preheated oven and roast for 35-45 minutes. You’ll know they’re done when they are tender enough to be easily pierced with a fork and the edges are beautifully caramelized and slightly crispy. About halfway through the cooking time, give the pan a shake to toss the beets for even browning.

Step 2: Prepare and Marinate the Chicken

1. Prepare the Chicken Breasts: While the beets are roasting, prepare the chicken. Place the chicken breasts between two pieces of plastic wrap or in a large zip-top bag. Using a meat mallet or a heavy rolling pin, gently pound the chicken to an even thickness of about 1/2 to 3/4 inch. This is the most important step for ensuring juicy, evenly cooked chicken.
2. Mix the Marinade: In a small bowl, whisk together the marinade ingredients: 3 tablespoons of olive oil, the minced garlic, chopped rosemary, thyme leaves, lemon zest, lemon juice, Dijon mustard, 1/2 teaspoon of sea salt, and 1/4 teaspoon of black pepper. Whisk until the mixture is well emulsified.
3. Marinate the Chicken: Place the pounded chicken breasts in a shallow dish or a large zip-top bag. Pour the marinade over the chicken, ensuring every piece is thoroughly coated. Let it marinate for at least 30 minutes at room temperature. For more developed flavor, you can marinate it in the refrigerator for up to 4 hours. (Do not marinate for longer, as the lemon juice can start to break down the texture of the chicken).

Step 3: Grill the Chicken and Assemble the Dish

1. Preheat the Grill: About 15 minutes before you’re ready to cook, preheat your outdoor grill or indoor grill pan to medium-high heat (around 400-450°F or 200-230°C). A hot grill is essential for creating those beautiful sear marks and preventing sticking. Clean the grill grates with a wire brush and then lightly oil them with a paper towel dipped in a high-smoke-point oil.
2. Grill the Chicken: Remove the chicken from the marinade, allowing any excess to drip off. Place the chicken breasts on the hot grill. Cook for 5-7 minutes per side. Avoid the temptation to move the chicken around too much, as this will prevent a good sear from forming.
3. Check for Doneness: The chicken is done when it is opaque all the way through and the internal temperature reaches 165°F (74°C) on an instant-read thermometer inserted into the thickest part. This is the most reliable way to guarantee perfectly cooked, juicy chicken that is safe to eat.
4. Rest the Chicken: Once cooked, transfer the chicken to a clean cutting board. Let it rest for 5-10 minutes. This crucial step allows the juices to redistribute throughout the meat, resulting in a much more tender and flavorful breast.
5. Assemble and Serve: Slice the rested chicken against the grain into thick strips. To serve, you can arrange the sliced chicken alongside a generous portion of the warm roasted beets. For a more complete meal, serve over a bed of fresh arugula, and garnish with crumbled feta or goat cheese and toasted walnuts. Drizzle with a little extra olive oil if desired.