In a bowl, mix together the crushed Oreos and melted butter until well combined. Press the mixture into the bottom of a 9-inch springform pan and bake for 10 minutes. Let cool.
In a mixing bowl, beat the softened cream cheese, sugar, and flour until smooth. Add the hibiscus tea concentrate and vanilla extract, and mix well. Beat in the eggs one at a time until just combined. Pour the mixture over the cooled crust and bake for 40-45 minutes, or until the edges are set but the center still jiggles slightly.
While the cheesecake is baking, make the candied pecan topping. In a small saucepan, mix the chopped pecans and granulated sugar over medium heat until the sugar melts and coats the pecans. Pour the mixture onto a parchment-lined baking sheet and let cool, then break into small pieces.
Let the baked cheesecake cool to room temperature, then refrigerate for at least 4 hours or overnight. When ready to serve, sprinkle the candied pecan topping over the cheesecake and slice into wedges.