For the ricotta, mix the cream, milk and buttermilk in a saucepan, stirring a few times gently over medium-high heat until it reaches 170°F (using a candy thermometer). You should see the milk solids form, separating from the whey (liquid). Remove from heat and rest 5 minutes. Scoop into cheesecloth set in a strainer over a large bowl and let sit until slightly cool and no longer dripping. Remove ricotta to a clean bowl. Season with sea salt. (You can refrigerate the ricotta in a lidded container for 3 days.)
Preheat the grill to medium-high heat or prepare coals. Meanwhile, add mustard powder, juice, sweetener, orange zest into a bowl and whisk together. Slowly whisk in the olive oil until vinaigrette has emulsified. (You can otherwise use a blender.)
Grill corn and then remove kernels. Grill bread until golden brown on each side. Pour vinaigrette over corn and add herbs. Season with salt and pepper.
To serve, plate the tomatoes, top with vinaigrette and a dollop of ricotta. Drizzle some honey around on the plate and serve with bread. Serves 6 or more.