Pat the chicken breasts dry with paper towels. Season both sides evenly with 1 teaspoon kosher salt, 1/2 teaspoon black pepper, and 1 teaspoon garlic powder.
Heat 1 tablespoon olive oil in a large skillet over medium-high heat until shimmering.
Add the chicken breasts to the skillet and cook without moving for 6-7 minutes until golden brown on the bottom.
Flip the chicken breasts and add 1 tablespoon unsalted butter to the skillet. Continue cooking for another 6-7 minutes, spooning the melted butter over the chicken occasionally, until the internal temperature reaches 165°F (74°C). Remove chicken from skillet and let rest on a plate tented with foil.
In the same skillet, add the sliced red bell pepper, zucchini, carrot, and broccoli florets. Sauté over medium heat for 5 minutes, stirring occasionally.
Add the minced garlic, 1/4 teaspoon kosher salt, and 1/8 teaspoon black pepper to the vegetables. Continue cooking for 2-3 minutes until vegetables are tender-crisp and garlic is fragrant.
Remove skillet from heat and stir in 1 teaspoon fresh lemon juice.
Slice the rested chicken breasts and serve alongside the sautéed vegetables.