Preheat the oven to 180°C / 350°F /Gas Mark 4 and line a 12 hole muffin tray with cases.
In a large mixing bowl combine the butter, oil, orange juice, orange zest, marmalade and vanilla extract. Set aside.
In a separate bowl, combine the flour, bicarbonate of soda and salt. Beat the eggs and sugar in another bowl with an electric hand mixer. Slowly add the butter, oil and juice mixture until well combined.
Add one-third of the flour mixture to the wet ingredients and beat until just combined. Add the rest of the flour and beat again, then gently fold in the pecans.
Carefully spoon the mixture into the cupcakes cases, filling each one about two-thirds full. Bake in the preheated oven for 25 minutes.
Remove from the oven and, while still warm, top each muffin with a little marmalade. Spread over the muffins and serve while still warm!
Serve warm for best taste.