Preheat the air fryer/ oven to 300°F (or 150°C).
Toss 4 oz cubed baguette with 1 tbsp olive oil, 1 tsp minced garlic, 1 tsp fresh thyme, 1/2 tsp onion powder, and 1/2 tsp garlic powder. Make sure to sprinkle the dry ingredients so every piece of bread is coated evenly.
Add the seasoned baguette cubes into the air fryer basket and spread them out in one layer. Air-fry for 13 minutes to make golden, crispy croutons. If you’re using the oven, spread them out onto the baking sheet and bake for 15 minutes.
Meanwhile, in a dressing bowl, whisk together 2 tbsp olive oil, 1 tbsp red wine vinegar, 1/4 tsp pepper, 2 tsp Dijon mustard, and 1 tsp whole grain mustard. Whisk until you no longer see two layers separating.
In a large salad bowl toss 10 oz halved cherry tomatoes, 4 oz sliced cucumbers, 0.5 oz sliced red onions, and 1 oz basil with the dressing.
To serve, add the crispy croutons to the bowl and toss quickly. Only toss the croutons right before serving or they’ll be soft.