Pour the vodka, blood orange juice, Cointreau, and simple syrup into a cocktail shaker filled with ice.
Shake to mix the martinis.
Strain into two martini glasses and garnish with an orange slice and maraschino cherry.
I used Absolut Vodka, but any premium vodka will work.
For even more citrus flavor use citrus vodka.
I used Cointreau, but triple sec will work as well.
I managed to cause the shelf in the kitchen cabinet to collapse and BOTH bottles of simple syrup crashed to the floor and shattered. I used agave nectar since they were smart enough to use plastic bottles that bounce. Either one will work.
If your oranges are really sweet, you may not even need to add any sweetener.