Preheat oven to 425°F. Cut a lengthwise slit down the center of the tenderloin to within 1/2- inch of bottom (careful not to cut all the way through). Open tenderloin so it lies flat. On each half, make another, lengthwise slit down the center to within 1/2-inch of bottom; cover with plastic wrap. Flatten to 1/4-in. thickness with a mallet.
Remove plastic wrap; spread the Thousand Island along one side of the pork. Layer the pastrami on top, then the Swiss cheese and sauerkraut along the center of the pork.
Roll up pork jelly-roll style, starting with a long side. Tie the roast at 2-inch intervals with kitchen string each about 12-inches long, then rub the pork with olive oil.
Combine the garlic powder, salt and caraway seeds in a small bowl; rub the mixture over the pork. Place on a rack in a shallow baking pan; bake, uncovered, at 425° until a meat thermometer reads 160°, about 35 minutes. Transfer to a serving platter or cutting board. Let it stand 10 minutes before removing string and slicing. Slice into 8 pieces.
In a mini food processor, combine all ingredients and pulse approximately 4 times to combine into a struesel mixture. Set aside or in the fridge until ready to use.
In one bowl, whisk together the flour, baking powder and salt.
In mini food processor, combine pecans and sugar and pulse to combine until it resembles wet sand. Four or fives pulses. Add this mixture to another mixing bowl. Whisk in eggs, melted butter, and milk. Pour flour mixture into this and fold to combine.
Fold in chopped apricots until just mixed together.
Let mixture rest for 30 Minutes. THIS IS A MUST! Muffins will not dome properly if they do not rest.
Pour into greased muffin pan. Sprinkle with streusel topping. Bake for 17-18 minutes, or until a toothpick comes out clean.
Let cool in muffin tin for 5 minutes before removing. Let cool completely before serving.