Historically speaking and even in the present day, Levantine communities are not big on butter on bread or toasted bread. Traditional forms of khubz include large flatbreads like taboun (named for the oven it is baked in), and since white flour was not really a thing in Palestinian communities until the 1960s or later, bread in Palestine in the 18th century would have been baked with locally grown and locally milled "whole wheat" flour. Palestine is a historically important wheat growing area, particularly in Marj ibn Amer (the Jezreel Valley). So first, there would be a difference in taste due to the flour difference. Palestine also was home to many varieties of heirloom wheat that are not commonly cultivated today or are almost extinct entirely. Different varieties of wheat have different bran-germ and protein ratios, lending themselves to different tastes. Second, flatbreads have a different texture even without "toasting." Rural households would generally bake their own bread daily; urban households might have their own tanour if they had the means, or they would go to a local bakery to buy daily. This is still the practice today, because flatbreads go stale much faster than loaf breads with a thick crust. So while households might "rewarm" the bread over a fire or stove, you still aren't going to get the same texture as true toasting. Finally, butter on bread wasn't and isn't a common thing in Palestine. Bread is usually eaten with olive oil. Butter from both cow and goat milk was part of Palestinian cuisine, but more for cooking and baking rather than eating straight on a piece of bread. Fresh butter that was more lumpy and almost yogurt-like in consistency (but without fermentation) might be eaten sweetened for breakfast.

Overall, I would say "buttered toast" would look and taste very different in 18th century Palestine than it would in the US today.