Chop 5-7 large heirloom tomatoes into small bite-sized wedges. Add them to a large salad bowl and season with 1/2 tsp kosher salt.
Prepare the peaches for the grill by cutting 7 yellow peaches in half and taking out their pits. Set your peaches aside until you’re ready to grill.
Cut 3 8 oz blocks of halloumi (24 oz halloumi) into planks for the grill or cast iron skillet. Set aside with the peaches until you're ready to grill.
Make the Dijon vinaigrette
Add 1 tsp Dijon mustard1/4 cup white wine vinegar3/4 cup olive oil, and a pinch of salt into a jar. Shake well.
Alternatively, you can whisk the mixture in a bowl but making the dressing in the jar makes storage easier since you won't use all of the vinaigrette.
Grill the peaches and halloumi
Cook the peaches and halloumi in batches on the grill or on a cast iron skillet until lightly charred. The timing will depend on the heat of your grill or skillet.
Remove the peaches and halloumi when charred to your liking and chop into bite-sized cubes.
Mix together the salad
Add the chopped peaches and halloumi to the large salad bowl with heirloom tomatoes. Drizzle a little bit of Dijon vinaigrette on top and mix well.
The tomatoes will have already let out their natural juices so don’t add too much vinagrette or else you’ll end up with a soggy salad.
Pick basil leaves off your bunch of basil and add them on top of your salad for extra flavor and decoration.
Serve with toasted or grilled sourdough bread or as is.