Place the bones in a baking dish large enough to hold all four bones and cover with salted water. Let soak in the water to remove blood and impurities for at least 5 hours to overnight. Remove the bones from the salt water and rinse them well. Pat dry with some paper towel and set them on a baking sheet.
Preheat oven to 375F.
Drizzle bone marrow with maple syrup and roast in the oven for 15-20 minutes until the marrow is slightly melted and bubbling around the edges and the maple has glazed the top.
Spread hazelnuts on a small baking dish and bake in the oven for 5 minutes until golden brown. Let cool, then finely chop them and reserve for later use.
While the marrow is in the oven, in a mixing bowl whisk together the lemon juice, red wine vinegar, honey, Dijon, and garlic. While continuously whisking slowly drizzle in the olive to form an emulsified salad dressing. Season with salt and freshly cracked pepper.
Toss the shallots, tomatoes and parsley in the salad dressing.
To serve place one pieces of bone marrow on a plate, spoon some tomato salad over top, garnish with hazelnuts and lemon zest. Serve with toasted country bread.