Prepare the dressing first so that it can cool down. Use a fork and really mix the pulp into the water to get most of the flavor. Then drain the tamarind water through a small sieve into a bowl. Discard the seed and remainder pulp.
In a small pot or deep pan, heat up the oil and add garlic, lemongrass and chili. Sauté until fragrant, then add the tamarind water. Add sugar and fish sauce, and taste to make sure the flavor is balanced. Set aside to cool down. Once it’s cooled down, add the chopped cilantro.
Bring a pot of water to boil and add the rice noodles. Boil for just a minute and immediately drain in a colander and rinse with cold water. Set it aside.
Heat up a pan with a tablespoon of grapeseed oil for minute or two. Over high heat, add the steak and pan fry for 3 minutes each side to be medium done for a 2 cm steak. Depending on the thickness of your steak, you might need to adjust the time on each side. Let it rest on a plate while you get the vegetables together.
Toss the carrots, cucumber, tomatoes, mint and noodles together, and mix in a tablespoon or two of the dressing (to your taste). Slice the steak and place the pieces on top of the veggie/noodles mixture. Spoon more dressing on top of the steak.