Prep the chicken and marinade: Pat the chicken breasts dry with paper towels (this helps them brown). In a small bowl combine 1 tablespoon olive oil, 1/2 teaspoon kosher salt, 1/4 teaspoon black pepper, 1/2 teaspoon dried oregano, and the juice and zest (about 1/2 teaspoon) of half the lemon. Rub the mixture all over the chicken and let rest at room temperature for 10–15 minutes. WHY: Drying the surface and adding a short marinade promotes a golden crust and infuses flavor without needing a long marination time.

Toast and rinse the quinoa: Place the dry quinoa in a fine mesh sieve and rinse under cold water until the water runs clear (this removes quinoa’s natural bitter coating, saponin). Optional: for extra nuttiness, heat a small dry skillet over medium and toast the drained quinoa for 1–2 minutes, stirring, until aromatic. WHY: Rinsing prevents bitterness; toasting deepens the quinoa’s nutty flavor and improves aroma.

Cook the quinoa: Add the rinsed quinoa and 2 cups cold water to a small saucepan with a pinch of salt (about 1/4 tsp). Bring to a gentle boil, then reduce heat to low, cover, and simmer for 12–15 minutes until the water is absorbed. Remove from heat and let rest, covered, for 5 minutes. Fluff with a fork and let cool slightly. WHY: Simmering gently and resting lets the grains steam through and gives the light, separate texture you want in a salad (not gluey).

Preheat grill or skillet: While quinoa cooks, heat a grill pan or outdoor grill to medium-high (about 400°F / 200°C) or set a heavy skillet (cast iron) over medium-high heat. Lightly oil the grate or pan. WHY: High, dry heat is necessary to develop a quick sear and caramelization on the chicken for flavor and attractive grill marks.

Grill the chicken: Place the chicken on the hot grill/pan and cook without moving for 4–6 minutes, until well browned. Flip and cook another 4–6 minutes until an instant-read thermometer inserted into the thickest part reads 160°F (71°C). Remove to a cutting board and tent loosely with foil. Let rest 5–7 minutes — the carryover heat will bring the chicken to a safe 165°F and redistribution of juices makes the meat juicy. WHY: Searing creates flavor through the Maillard reaction; resting prevents the juices from running out when you slice.

Make the dressing: While the chicken rests, whisk together the remaining 1 tablespoon olive oil, juice of the remaining half lemon (about 1–2 tablespoons), remaining 1/2 teaspoon dried oregano, a pinch of kosher salt and a few grinds of black pepper in a small bowl. Taste and adjust for acidity or salt. WHY: A simple lemon-olive oil dressing is bright and lets the fresh ingredients shine without overpowering them.

Assemble the salad base: In a large mixing bowl combine the slightly cooled quinoa, arugula, halved cherry tomatoes, and sliced cucumber. Drizzle about half the dressing and toss gently — you want the grains and greens lightly coated so they stay vibrant and not soggy. WHY: Tossing while the quinoa is warm helps it absorb a touch of dressing and meld with the other textures.

Slice the chicken and finish: Thinly slice the rested chicken across the grain. Arrange the slices over the quinoa-arugula mixture, sprinkle the crumbled feta evenly, and drizzle the remaining dressing over the top. Finish with a final grind of black pepper and a small pinch of flaky sea salt if you like. WHY: Slicing across the grain yields tender pieces; finishing with flaky salt and fresh pepper adds contrast and a restaurant finish.

Serve and store: Divide the salad between two plates and serve immediately. Leftovers: keep dressing and chicken separate if possible and store in an airtight container in the refrigerator for up to 2 days. WHY: This salad is best when the quinoa is warm or room temperature; separating components helps preserve texture.