Slice the red and yellow peppers into 1/4-inch thick strips, cut the zucchini into 1/2-inch thick half-moons, and trim the woody ends from the asparagus before cutting into 2-inch pieces. Mince the garlic cloves and measure out the salt, pepper, thyme, and lemon juice. Having everything prepped and ready will allow you to work quickly once the pan gets hot, ensuring the vegetables cook evenly and maintain their bright color and crisp-tender texture.

Heat the olive oil in a large skillet over medium-high heat until it shimmers, about 1-2 minutes. Add the red and yellow pepper strips and sauté for 2 minutes, stirring occasionally. The peppers should begin to soften slightly while maintaining their bright color and slight crunch. I like to use medium-high heat for vegetables like peppers because it helps them develop a subtle caramelization while staying crisp.

Stir in the zucchini and asparagus pieces from the mise en place and cook for 6 to 7 minutes, stirring occasionally. The vegetables should become tender but still maintain some bite—the zucchini will soften and lighten in color, while the asparagus will turn bright green. This timing allows the longer-cooking zucchini and asparagus to soften properly while the peppers don't become mushy.

Add the minced garlic, salt, and black pepper from the mise en place and cook for 1 minute, stirring constantly. The garlic will become fragrant and distributed throughout the vegetables without burning, adding a pungent depth to the dish. I always add garlic near the end of cooking rather than at the start because it can burn easily and turn bitter at high temperatures.

Remove the skillet from heat and stir in the butter and fresh thyme, allowing the residual heat to melt the butter into the vegetables. Add the fresh lemon juice and toss everything together gently. The butter enriches the dish with a subtle richness, the thyme adds an herbaceous note, and the lemon juice brightens everything while enhancing the natural flavors of the vegetables.

Transfer the sautéed vegetables to a serving dish or individual plates right away. The vegetables are best enjoyed hot when their textures are at their peak—tender yet still slightly crisp, and their fresh flavors are most vibrant.