Thai Beef Salad (Charred Sirloin Tossed in Lime-Fish Sauce)

Let 260 g beef sirloin stand at room temperature for 10 minutes and pat the surface dry. Heat a pan thoroughly over high heat and sear the beef for 2 to 3 minutes per side as an initial timing guide. Do not use time or surface color alone to determine doneness. Check the thickest part with a food thermometer and continue cooking until it reaches at least 63C. Rest the cooked beef for 5 minutes. Meanwhile, thinly slice 60 g red onion. If its bite is strong, soak it in cold water for 5 minutes and drain it well. Cut 100 g cucumber and 120 g tomato into bite-size pieces. Mix 1.5 tbsp fish sauce, 2 tbsp lime juice, and 1 tsp chili flakes for the dressing. Slice the rested beef thinly and tear 12 g mint immediately before mixing. Toss the beef, cucumber, tomato, and red onion gently with the dressing, then add the mint and turn the salad once more. Serve before the beef becomes cold. The required pan time changes with the steak's thickness and the pan's heat, so the temperature reading governs rather than the suggested 2 to 3 minutes. This ingredient list has no separate salt; the measured fish sauce dressing provides the seasoning.