Pat the chicken breast dry with paper towels and season both sides evenly with the sea salt, black pepper, and garlic powder.
Heat 0.5 tbsp of extra virgin olive oil in a stainless steel or cast iron skillet over medium-high heat until shimmering.
Place the chicken in the skillet and sear for 6-7 minutes per side until the exterior is golden-brown and the internal temperature reaches 165°F.
While the chicken is cooking, cut the sourdough bread slice into bite-sized cubes.
Remove the chicken from the pan and let it rest on a cutting board for 5 minutes.
Add the remaining 0.5 tbsp of olive oil to the same skillet, then add the sourdough cubes.
Toast the bread for 3-4 minutes, stirring frequently, until the croutons are crisp and have absorbed the savory pan juices.
In a large bowl, toss the fresh arugula with the lemon juice.
Slice the rested chicken into strips and serve over the arugula, topped with the warm sourdough croutons.