• In a medium saucepan, heat the oil over medium low heat.
• Once heated, add the chopped onion and cook, stirring often, until softened and starting to turn golden around the edges.
• Stir in the garlic and cook just until fragrant, 30 seconds to 1 minute.
• Stir in the tomato paste and cook just until heated through.
• Add the diced tomatoes and stir well to combine.
• Once heated, stir in the baking soda and continue to stir while the mixture foams.
• Once the bubbling decreases, add the water, curry powder, brown sugar, vinegar, Worcestershire sauce, paprika, salt, and black pepper, then stir to evenly combine.
• Add the cinnamon stick and simmer, stirring occasionally, for about 10 minutes to allow the flavors to blend.
• Remove from heat, discard the cinnamon stick, and use an immersion blender to puree the sauce until smooth or carefully transfer to a stand mixer and blend until smooth.
• If too thick to blend or if you want a thinner sauce, add a splash or so more of water and blend again.

While the sauce is simmering, prepare the Bratwurst:

• Cut small slits across the cooked Bratwurst about 1/2 inch (1.25 centimeters) apart.
• Place a pan over medium heat and drizzle with a thin layer of vegetable oil. Add the Bratwurst and cook until deeply golden and crisp on each side.
• Serve the Bratwurst whole or cut down the slits to make individual pieces.
• Top the Bratwurst slices with the warm curry tomato sauce, sprinkle with more curry powder, and serve immediately with fries or Brötchen.