In a small non-stick pot over medium heat, add 1/2 cup sugar and 2 tbsp water. Stir to combine. Bring to a hard boil and let it cook for 6 - 8 minutes. Swirl the pan every couple of minutes to make sure all of the sugar is being incorporated. Check the color. The sugar should be a light amber color. (You just made caramel!)

Add 1/3 cup fresh lemon juice, all at once. Stand back from the pan while doing this, just in case it splashes. It will bubble rapidly when the liquid goes into the caramel. Stir well and let it cook for an additional 3 – 4 minutes to reduce slightly.

Add salt and thyme sprigs. Stir again and remove from heat. Set aside to cool slightly.

In a medium pan, heat 1 tbsp olive oil over medium heat. Season fish with salt and pepper.

Place fish gently in pan and cook for 4 minutes without disturbing. Flip fish and cook for an additional 3 – 4 minutes.

Remove from heat and let rest for 1 – 2 minutes. Drizzle gastrique on plate, or over fish, and serve.